[H] X2 problems

[Thane Sherrington (S)]

Ok, I can't figure this out, so I'm turning (once again) to the 
Collective.  I have a customer with an AMD X2 3800+ system.  In the 
shop it runs fine:  I've run Burn-In-Test Pro 4 and 5 for 110 hours, 
I ran UT2004 in demo loop for 50 hours, and I ran various Photoshop 
benchmarks.  Then I just used the computer for eight hours.  I also 
left machine sitting overnight idle several times.

At the client's site, the machine locks (first the mouse stops 
responding but one can still tap the numlock and have response from 
the keyboard for a few seconds and then it locks as well) randomly 
one to four times a day.  Sometimes it spontaneously reboots, and 
occasionally blue screens (with an 0x0000007D error.)  That error 
suggests RAM as a problem, but MemTest says no problems in 40 passes.

Here's my question:  Can a bad USB or parallel device cause this sort 
of problem?  Is there anything else I'm missing?

T