Well I'm stumped... Maybe a partition wipe and an OS reinstall then...
Over to others...

Did you install the latest built of your video card driver recently?

stonehedge
Did you install the latest built of your video card driver recently?

Most recent build installed as a result of DriverBooster but no difference between previous build and most recent build.

You might want to check the drivers by going to the manufacturers websites, driverbooster is good, but no substitute for actually visiting the websites for each peripheral manufacturer (it is time consuming of course)... Thanks..

I may have missed this in the thread, so my apologies if I did. Have you tried re-installing the 64 bit X3d patch as administrator, yet? Not an uninstall, but a simple re-install of that patch as administrator? That patch includes SONARPDR.exe, so is a simple test to try (it is possible the original patch did not install correctly).
 
It may be worth downloading the patch a second time as well, just in case.

Here's a thought, I do have one hdd that is an ide (pata) drive connected to a Jmicron JMB363 controller built-in to the motherboard (an Asus P7P55D Pro).
This is not the os drive, not my project drive nor my sample drive. It's a misc drive.
Could that be an issue?
Should I replace it with a sata drive and disable the Jmicron controller in the bios?

Well you should be able to test with it disconnected?

CakeAlexS
Well you should be able to test with it disconnected?

I was checking first to see if anyone has any first hand knowledge before I shut it down, open the case and disconnect it.

If you've updated your video card driver recently...that might be the culprit.  I recently updated mine (Nvidia GTX560ti).  I was rendering a video in Sony Vegas Pro that HAD to be done the next day and it would not render.  Would get half way through and just stop and white screen....in the exact same spot every time.  It was a photo montage, so I thought it might be the particular photo it was locking up on causing the problem.
 
Come to fine out...it was the nvopencl.dll causing the lockup (I knew this via the error box that came up when Vegas would lock up).  I did a quick search on the dll file and found the answer in the Vegas forum.  I had to disable a certain feature (can't remember it off hand) in the preferences.  The video rendered without a hitch after that.

Since the issue is only happening in the 64Bit version of Sonar X3, could the issue be related to a problem when scanning a 32Bit plugin?