.... All drivers from the previous mobo were removed before installing on the new mobo, as well as upgrading the remaining drivers to the latest version. Windows 7 was NOT reinstalled after transferring the HDD to the new mobo. Yea, I know I should have, but I had upgraded to Win 7 only a short time ago and was hoping to avoid a complete installation....
No yellow/red flags in Device Manager
No Problem Devices listed in System Information
under the Component tab?
Back up an image of your drive, then scan the system files
for problems. If that doesn't work perform a non-destructive OS repair install
If that fails then maybe it really is a hardware problem. I'd perform a CMOS reset (per your service or MB manual) before doing anything else at that point.
How often does this occur per day? Any way to reliably trigger it?
Install HWMonitor and look at the readings at idle and then under load.
If it happens within 2 hours of use reliably then boot up Ubuntu or Mint ("LiveCD") and run it in memory playing around with it (after all its a test drive) for a couple of hours. No freezes = OS, driver, startup app or boot drive responsible. Runing Windows in Safe Mode would rule out many drivers and startups. Freeze still = hardware. Test boot drive with mfg. diag app (WD DLD).
Next step would be an external minimal build to rule out parts and hopefully rule in parts. Need to know what other parts you have available to swap test and any compatible PC you may have to test bed suspect parts? Also, do you have a volt-olm meter?