So, almost on command, I can get my 64-bit X1d to crash and/or "pop" with the audio going dead (also evidenced by huge spikes in the Kontakt player outputs) by freezing/unfreezing, bouncing to tracks...basically anything "new" I add to the project after it's been going the same way for a while.  I suspect a few 32-bit plugs...really not sure.  When the "pop" happens, it'll play either with silence or a weird droning frequency...I just close the project and reopen it and it's fine.
 
When the "crash" happens, either X1 won't reopen because it's still open in task manager, I'll get the "stopped working" message, or when I try to reopen without rebooting will get the "no audio devices for the current model" message, both requiring full computer reboot. Also, after the reboot, it takes a VERY long time for a project to load.  A quick look at task manager during one of these adventures shows bitbridge action all over the place, usually one MUCH higher than the others...I also see my first core "spike" (of 8) from within X1 always the highest, sometimes hitting red briefly.
 
Anyone experience similar?  I read plenty about 32-bit issues with 64-bit installs, but honestly it's been pretty good until recently.  I'm trying to figure out if it's the plugs, the way bitbridge is allocated (I have it set to default, whatever that is), my soundcard/drivers (Roland Quad Capture), a combination, or....whatever.
 
Just figured I'd come on here and brainstorm to see if anyone has felt/is feeling my pain.  Thanks in advance for any insight.

You could try removing the 32 bit plugins, reset and rescan and see what happens.
 
"no audio devices for the current model" - this smell of dodgy interface drivers (up to date?) and/or a firmware revision may be needed. Have you checked the Windows event viewer?

Holy cow...I just peeked at the Windows Event Viewer...which I didn't knew even existed...and there are over 2000 events.  Some are Sonar "program hangs", a lot are bitbridge things like:
 
Faulting application name: BitBridge.exe, version: 1.0.5.1185, time stamp: 0x4aed8921
Faulting module name: ntdll.dll, version: 6.1.7601.18229, time stamp: 0x51fb1072
Exception code: 0xc0000005
Fault offset: 0x00033307
Faulting process id: 0xfd0
Faulting application start time: 0x01cec142a6281d25
Faulting application path: C:\Program Files\Cakewalk\Shared Utilities\BitBridge.exe
Faulting module path: C:\Windows\SysWOW64\ntdll.dll
Report Id: 8c7da0d0-2d3c-11e3-8f52-5cf9dd6b31ce
 
And more weirdness from ethernet connection (that I DON'T HAVE CONNECTED):
 
Broadcom NetLink (TM) Gigabit Ethernet: The network link is down.  Check to make sure the network cable is properly connected.
 
Ideas?  You seem smarter than I am...  =)  Thank you

Keep the LAN cable connected into the PC, if you don't want internet DISABLE the adapter in device manager by right clicking the adapter.
 
Hmm looks like you are on the right track with those 32 bit plugins. Close Sonar. Create a folder call plugins. Under there create a folder called 32 bit, and another called 64 bit. Copy the relevant DLL's across to relevant folders. Change your vst paths to point to the correct (new) folders, remove the old file paths (take a note of it). Reset and rescan Cakewalk. At first don't put any 32 bit plugins in, then later throw them in one by one to see what happens.
 
Or take an executive decision like me and refuse to use 32 bit plugins.
I'm not sure if bitbridge logs the crash anywhere so you can get more detail, maybe others can chirp in.

what 32bit plugs are you using? from my experience it sounds like its Bitbridge. X1 64 did not always play nice with 32bit plugs. I would also check the buffer settings on the QuadCapture they could be too low.

caminitic
So, almost on command, I can get my 64-bit X1d to crash and/or "pop" with the audio going dead...

Yes, I have this exact symptom. I'm using X3C and Windows 8.1.
I have isolated it to two 32 bit plug-ins in my project: 2 instances of "Flux Bittersweet V2".
Removing the plug-ins makes the problem go away.
I just noticed on the Flux page that Bittersweet V3 is available and is 64 bits (Thanks Flux!) so I'll be downloading and installing the 64 bit version and I expect the problem to go away.

After going 64-bit OS and Sonar, I had tons of problems with 32 bit plugs.
Dropped all of them but one.  Unfortunately I have still had Cpu spiking problems along with popping and latency problems that I now believe is 
the result of Focusrite's USB ASIO drivers.

I am wondering if your audio device is locked up due to the hanging tasks when you crash.
 
It seems quite evident that one or more 32-bit plug is not a happy camper with BitBridge, in Sonar x64.
 
Here are some options:
 
1.  Find and swap out the plugs causing the issues, removing errant ones from Sonar x64.
2.  Eliminate BitBridge altogether, by switching to Sonar x32 for these projects.
3.  Purchase JBridge, to see if that works better with 32-bit plugs than BitBridge
4.  Look for 64-bit update availability for problematic 32-bit plugins.
5.  Eliminate all 32-bit plugins in Sonar x64.  (while this is an option, I would not automatically abandon 32-bit plugins that are working ok in Sonar x64, and do not actually recommend this option).
 
However you get to a place where you have a more stable system, I would recommend you consider moving to a completely 64-bit set of plugins as is possible, even if you end up with some set of 32-bit ones that continue to work in 64-bit Sonar.  I have done this, where possible, and only use certain 32-bit plugs for which I currently have no 64-bit replacement plug available.
 
I'm too sleepy to think of anything else for the moment - hope the above is of some use in coming up with a game plan.
 
Bob Bone
 

What Bob and I said....