And do not delete the aud.ini..if you are opening older sonar projects...just rename it for now....and if you can no longer open older files from a younger Sonar version, that were opening pryor to the rename, if so.....you can rename the Aud.ini back to its original state to regain that status back.

Hello, Sir Les.  Thanks for your reply. 
1) I have Windows Sounds set to "No sounds".
2) This DAW is not connected to the Internet.  Consequently, I have no anti-virus programs installed on this computer.  The Win 7 Firewall function is on the computer.
3) Full DAW specs
Processor - Intel i5 3570 Quad core 3.40 Ghz - running at standard speed, not overclocking
MOBO - ASUS P8Z77-V LX w/ Intel Northbridge Z77 Express chipset
Drives - 2 x Seagate ST500DM002 Barracuda, 500 GB, 7200 rpm, SATA-6G
Memeory - 2 x Corsair Vengence CMZ16GX3M2A1600C10B (2 modules of 8 GB apiece: total 16 GB), DDR3
Power - Corsair CMPSU-750TXV2, 750 watts
Firewire - StarTech.com 4 port PCI 1394a  firewire card
OS - Win 7 Home Premium 64 bit, SP-1
Cakewalk - Sonar X2a (I believe I have all Sonar X2 updates installed)
 
4) I am indeed opening older Sonar projects, so I appreciate the tip about renaming the Aud.ini file.  I assume the Aud.ini file is located in the main Cakewalk folder?

The Mackie units are pretty fussy about the specific TI Chipset Firewire Controller.
IOW, Not just any TI chipset controller will work well.
 
From what you describe (somewhat random freezes) a bad stick of RAM would have been a likely culprit.
If that's not the case, I'd take a look at the Firewire Controller.
The SIIG TI Chipset controller works well with the Mackie units.
The less expensive Syba TI Chipset Firewire Controllers do not.
 
If you're running a Firewire audio interface... and you're experiencing issues (and you've ruled out RAM and other sources of instability), the Firewire controller is another likely culprit.

Hello.  Thanks for your input Jim R.
 
1) I ran Memtest+86 for 2 complete cycles, and no errors were reported.  This suggests the memory is ok.
2) Other than ram problems, what "other sources of instability" should I check on?
3) How do I identify my TI chipset firewire controller?  Under Device Manager > IEEE 1394 Bus host controller, what is listed is "Texas Instrument 1394 OHCI compliant host controller", and under Properties for this device it simply says "Texas Instrument 1394 OHCI compliant host controller".
 
Thanks again.

Hello.  The firewire card in my computer is a StarTech.com brand.  On their web-site for this card, they list the following information:  "Chipset ID - Texas Instruments - TSB12LV26".

From what I know about TI and/or compatability standards with firewire IEEE 1394...if you update to firewire IEEE 1394b 400/800 you get a better chip ...still have to research the best recommendation of chip for your audio device, but the newer 800 IEEE 1394b 400/800 cards I believe have solved some of the problems 400 IEEE 1394 had.
 
What does the manufacturer of Your audio interface recommend?

Hello, Sir Les.  That is a good question, and I don't know the answer.  I will check on the Mackie website to see what they recommend there.
 
Sadly, my Makcie Onyx 1604 mixer with firewire card installed is now a legacy device.  Mackie has since moved on to building a 1604 mixer with the firewire capabilities built into the mixer, so they may not have recommendations for my device.
 
I really hate that about digital sound hardware and software: you find out ofter you purchase it that the lifespan of the device is limited by upgrades to computer hardware, changes to the OS, or the maker simply no longer supports the device.

I know it may be necessary to upgrade, But at this point, let us not jump to any conclusions on IEEE firewire.
But was thinking more in line with the computer IEEE being needing a upgrade...not your audio device...althought the audio device needs to be connected to a IEEE port on the computer...legacy or not....and should work.
But those legacy drivers for the computer may not have been worked out well enough...So making a jump to a IEEE b 800 card which usually are backwards compatable or have a 400 port with a newer bug reduced state chip may help some , ...
 
Let us see some system Info Please....Could be just a conflict with IRQ's...or a app running in background.
 
So before we jump to conclusions on the firewire problematics being the X factor,...which is working?....let us get some info about your system setup.
 
You can copy paste some up by going to ...start button/all programs/Accessories/system tools/ system information click on conflicts and sharing Tab, . when it shows up..copy and paste.
 
Also go to IRQ's Tab and post that up...also check the Software Environment/ system Driver status , and make sure they are all OK.
 
Then we can move to other things which may point out the culprit.

EltonJohn
Sadly, my Makcie Onyx 1604 mixer with firewire card installed is now a legacy device.  Mackie has since moved on to building a 1604 mixer with the firewire capabilities built into the mixer, so they may not have recommendations for my device.
 

 
Mackie Firewire units are particularly fussy about the Firewire controller.
Get a SIIG TI chipset controller.  They're more expensive... but it'll work.
 

Well I would contact the Mackie People on that, before buying more of..and make absolutely sure,,,.( no sense going out and buying cards that may...or may not work, if you can avoid doing so.)...for my Firewire solution, and Allen and Heath desk,... I followed the manufactures advice on upgrading to a 400 / 800 card and TI chipset, they had a list to follow of Great, good to fair, and ones to stay away from...So I hope you find some resolve with your Question as to what is necessary for Your Mackie...from Mackie...that way you are sure it is correctly done .