Please help! Getting lockup AFTER quitting Orthos/Prime95!

This is driving me nuts. I just got done running Orthos for 6 hours. Stopped it to see if I could get a little more aggressive. I bring up uGuru and the computer locks up on me (about 20 secs after quitting Orthos). What is going on here?!?!?!?! It happened a few times before but I blew it off as tight memory timings or not enough vcore, vmem, etc. I tried to set everything up so I could eliminate those as problems:

VCore 1.44 in bios. 1.37 in CPUz
FSB 455
Max Temp after running Orthos for 6 hours, 63c (was usually around 58-61)
Memory: 5-5-5-18 at 2.2v
I also had MCH and CPU VTT up a notch or 2

Any ideas???? Please help!

Does it lock up at stock settings? Have you checked to make sure both instantiations have quite when you stop Orthos? It should do it itself but I'd check.

Is there a bug w/ uguru by chance? Do you have the latest version & BIOS? Any other programs giving you issues?

Do you have problems after using the BIOS instead of uguru to OC?

Is there any chance you have EIST and C1E enabled in the BIOS? Sounds like it is dropping the volts too much and crashing