Hello.  Sorry about the long post.  I am running Sonar X2a (64 bit) in Win 7 SP1 x64.  For a year now (since buying Sonar X2 summer '13) I have been having a problem with intermittent computer crashes when using Sonar.
 
The Crashes.  Intermittently, when I use Sonar, the computer will freeze up – the graphic display freezes, and the computer no longer responses to mouse or keyboard activity.  The computer will not respond to Ctrl-Alt-Delete.  To regain control of the computer, I must hold the power button to hard-stop the computer, and then re-start it.  Because these crashes bring down the OS, there is no error log recorded; WhatIsHang records no problems.  I can sort of reliably cause a crash problem by starting the computer, launching Sonar, load up a project, and then walk away from the computer.  When I return to the computer after 60 minutes or so, typically the computer is crashed/frozen.  So I get crashes/freezing just simply by having Sonar up and running on the computer; I don't even have to interact with Sonar to get crashes/freezing.  I also get crashes/freezing when recording, playing back, and editing audio or midi data, and while doing other work in Sonar.
 
Interestingly enough, on a hunch I started the computer today, launched my copy of Pyro Audio Creator 1.5, opened the Editor application and then loaded an mp3 file, and then walked away from the computer, the computer was crashed/frozen when I checked on it about 40 minutes later.
 
HOWEVER, I can start the computer, launch Sound Forge 10, load up a .wav file, and the computer will run fine for 3-4 hours, without any crashes/freezing.  Indeed, the computer will run reliably for hours without problems whatsoever so long as I am NOT using Sonar or Pyro.
 
What I have done to try to resolve this:

1. Updated Sonar X2 with the latest update
   
2. Updated Win 7 with latest patches/updates
   
3. Updated drivers for audio and midi interfaces to the latest drivers available
   
4. Updated the bios to the latest version.
   
5. Re-built the entire software environment by formatting all HDs, re-installing the OS and re-installing programs (making sure each installer was “run as Administrator”).
   
6. Put in a new Siig DP FW card (with TI XIO2200AZGW chipset)
   
7. Ran MemTest+86 (ver. 5.01) for two complete cycles.  Zero errors were reported.  (Note also that this process took 4+ hours, and the computer did not crash during this time.)
   
8. Because intermittent computer crashes are commonly caused by memory problems, I also swapped out my memory modules.  My computer has two memory modules, and I got the same crashing/freezing behavior using both memory modules and with any one of the memory modules.
   
9. Monitoring CPU and MOBO temperatures: the CPU temperatures stays round 36-37oC – well within normal operating tolerances; the MOBO temperatures are a little cooler, and also well within normal operating tolerances.
    
   

Still to do: stress-test the CPU using Prime95.
 
So, my suspicion at this time is that there is some interaction of Sonar or Pyro with the audio interface that is causing these crashes/freezes.  I am hoping that some user here can suggest some tweaks to Sonar, the OS, or the audio interface that will help with these crashes/freezes.  Or maybe someone has another idea for trouble-shooting things I can do to further isolate and identify the problem.
 
The Computer
 
I built the DAW specifically to run Win 7 and Sonar X2.  The computer has no other functions, and is not online or networked.  The specs are as follows:
 
Processor – Intel i5 3570 quad core @ 3.40 gHz (normal clock – NOT overclocked)
MOBO – ASUS P8Z77-VLX w/ Intel Northbridge Z77 Express chipset
Memeory - 2 x Corsair Vengence CMZ16GX3M2A1600C10B (2 modules of 8 GB apiece: total 16 GB), DDR3 Power - Corsair CMPSU-750TXV2, 750 watts Firewire – Siig DP FireWire 2-port PCIe card
Drives - Seagate ST500DM002 Barracuda 500 GB, SATA 7200 rpm HDs OS - Win 7 Home Premium 64 bit, SP-1 Cakewalk - Sonar X2a (I believe I have all Sonar X2 updates installed)
Audio Interface – Mackie Onyx 1604 w/ firewire card installed (driver ver. 1.7 installed – is the only driver version Mackie makes for this device and this OS)
MIDI Interface – MOTU Micro Express USB midi interface (Motu “universal” driver installed – is the only driver version Motu makes for this device and this OS).
 
Note: this computer has no VGA card. All graphic functions are handled by the CPU itself.
  
Any ideas?  Thanks for reading.

There will be a GPU on board the motherboard. The drivers may need updating for this.

When you ran windows autoupdate did you look at installing the optional updates as well. This can resolve library issues.

Consider doing a vst RESET followed by rescan.

Also check intel auto update.

Oh check for firmware updates on your hard drives.

And check windows event viewer.

You may want to consider putting in a branded graphics card to see if it helps...

Looks like a hardware or related to hardware issue to me (not Sonar).

Is not the Mackie a audio interface with known issues with the drivers? Just askin'. 
I'm sure I've read stuff in the hardware forum where owners were pi--ed off about Mackie never supporting the board with good ASIO drivers. So typically it's one of theose products that might work with a Mac or Audacity but not with a DAW like Sonar which need the "good" drivers to function properly. 
 
You've covered most your bases for the computer, Did you ever run a DPCLAT test? 
http://www.resplendence.com/latencymon
 
But the one thing you haven't done as far as swapping out components is to try a different audio interface. I'll put my money on that solving the problem. 
 
From A gear Slutz thread: 
 
http://forum.dawbench.com...mance-Data-Base/page13
 
Mackie Onyx 1640i : Heres one I had been sitting on for a while as I didn't have the measured RTL values and the reported nominal values were, hmmm, very optimistic. I finally had the opportunity to get in front of one again to do the RTL calculations. Wow, in short the settings values have absolutely no correlation to what is delivered and even more concerning was I could not get a consistent result from the RTL utility, with the value swing around up to 80 samples at a time. Check out the cart for the actual delivered RTL , I have no idea how the DAW's could possible compensate for that amount of variance , absolutely unworkable IMO
 

Thanks AlexS, for your suggestions.  I can tell you the Windows Event Viewer records no events - I think this because when the crash/freeze happens, it brings down Windows, so Windows is unable to record any event.
 
The drivers for the MOBO have all been updated to the most recent versions - presumably including any GPU drivers.
 
Obviously it is not clear whether this is a software issue or a hardware issue.  If it is a hardware issue, then I would expect to see crashes/freezes when using any software (certainly Sound Forge), but I have not seen this behavior.
 
I will make the updates you suggest and see what happens.
 
Johnny V. -  The drivers for the Mackie firewire deice are ASIO drivers.  It could be a problem with the Mackie drivers - I have to set aside some time to call Makcie Tech Support to pick their brains about this.  I am not aware of Mackie having more or fewer problems than other audio interface makers.  I am not going to lightly get rid of the Mackie - it would cost a lot of money to replace, and plays a central role in my music space.  If I knew for certain that the Mackie drivers were a problem, it makes equal sense to change the recording software to work with the Makcie as to replace the Mackie to work with the recording software,

I'm with Alex on this one. On-board graphics cards have been known to create all sorts of issues and I think it's definitely worth slotting in a 3rd party graphics card to take this out of the equation. Let us know if this is an option for you, and how you get on.

Thanks rebel007 - adding a graphics card is definitely an option.  It would certainly be easier and less expensive to add a graphics card than to replace my mixer or my computer.
 
I don't do special video editing, just do audio editing.  Can you give me any guidelines on a suitable stable graphics card to get?

Before getting too carried away with complex fixes (i.e. new hardware), it seems like these crashes are occurring when the system is idle (i.e. no interaction from you), yes?
 
If so, Win7 is not elegant at all with its power management, please be sure that Win7 is specifically told never to idle anything or hibernate (and always have it connected to a power supply if a laptop). Additionally, Win7 will idle USB ports, but this usually doesn't manifest itself until coming out of a hibernate situation (i.e. hardware will not connect). Another generic thing to look for is "tasks" by software that occur when "idle." Some programs do this (like anti-virus checks, software updates, etc.)
 
If Win7 is set to hibernate/go idle, it may be possible to just set that time to something reasonable and sit near the machine as it goes idle and see if any programs create a popup, but seems unlikely as this freeze has occurred without a restart for you.
 
Unless driving 3D programs (SONAR is 2D), the graphics should not be an issue as far as usage, but driver conflicts may be.

As you've no doubt already deduced, this problem has nothing to do with SONAR. It is either a hardware or a hardware driver issue. Something at the kernel level is waiting for a process to complete that never does, such as a hardware interface that doesn't respond to an action request. Only the lowest-level processes can completely hang Windows to the point where it cannot respond to other hardware input such as mouse and keyboard events.
 
That generally means a driver, but it's not necessarily the fault of the driver. More likely, it's an interface device (audio, video, disk, network, etc.) that's getting hung while attempting to respond to its driver. And that's nearly always due to broken hardware.
 
It could also be the motherboard, power supply or CPU, any of which can have heat-related intermittent problems even though the reported temperature is OK. The clue for that kind of problem is that the likelihood of hangs increases the longer the computer has been on, is more frequent on hot days, or when the skins are off (you'd think running without side panels would cool things down, but it actually messes up the airflow).
 
Some things you can do first...Vacuum out everything, including the power supply fan, CPU fan, and the CPU heatsink. Pull out all interface cards from the backplane, clean their edge contacts with a pencil eraser followed by alcohol and re-insert them. Disconnect and re-connect every hard drive cable, both data and power. You've already removed and re-seated the memory cards.
 
Mettelus has a good point, too: make sure your USB ports are not allowed to power down when idle.

I would opt for a separate video card, even a low level one.  I have an i7 CPU in my main system and had some video problems.  A separate video card fixed those.   My backup system is an ASUS P8Z77 LE Plus motherboard and an i5 3550 CPU with 8 GB of RAM - similar to your system.  My Windows experience with the Intel video was 3.2.  I installed an old NVIDIA GTS450 OC video card and the Windows experience jumped up to 6.5. 
 
I'm not using the "Lucid Virtu" video software supplied by ASUS.
 
Expansion cards, e.g. your PCIe firewire card, can also cause hang ups.  Not specifically the PCIe card you have, just expansion cards in general are one potential area.
 
I do some PC support and try to avoid recommending BIOS upgrades, but with the problems you are having, I would update to the latest ASUS BIOS. The latest BIOS update, 9/19/2014 states "Improve System Stability".

Thanks mettelus - I have Win 7 set so processor and HDs never hibernate/sleep.  I have to check on the USB port power settings.  I don't believe I have any software set to do things on a timed basis: no anti-virus program other than Win 7 on tis DAW and no automatic computer software updates.
 
Thanks biflipper - The situation is a little more complex than only happening when idle.  I have had crashes/ freezes when interacting with Sonar, but they happen intermittently.  By launching Sonar and then leaving the computer sitting idle, I tend to get crashes/freezes to happen more reliably - but never 100% of the time. Yet, with Sound Forge up and running for hours, I never have crashes, either interacting with Sound Forge or when Sound Forge is left sitting idle.
 
I had previously gone through the process of remove all the computer components and re-seating them to try to fix any loose connections.  I continue to get intermittent crashes.
 
I have not noticed more crashes on warm days or after many hours of usage.  The crashes/freezes can occur soon after turning on the computer or anytime thereafter.
 
But yes, it seems highly likely that there is a hardware malfunction.  So one solution I am contemplating is to buy a new MOBO and processor, and rebuild.  Obviously, I hope to avoid doing this.
 
I have previously updated the bios to the latest ASUS version.