Computer crash & artifacts

[xoahzarodx]

Problem:
Sometimes when I play Crysis/GTA4 etc (high demand games I suppose). The screen would suddenly freeze and crash to desktop. After that when I try to play audio or video files, they are filled with artifacts(crazy colour lines and crazy noise). Windows doesn't crash but most programs have some problems and crash. The problem disappears when I restart.

Specs:
MSI Twin Frozr II 5850 @1.154V 745/1000
AMD Phenom II 1055T @3.5GHz 1.375V Turbo Boost off
A-Data 1600Mhz XPG Gaming series
WD Caviar Black 1TB as system drive
Antec Truepower New 750W
Windows 7 Home Premium

Possible thoughts:
Overheat? Once I checked with CPUID monitor after a 'crash' and it's 35C/47C for CPU/GPU respectively, so maybe no.
PSU? Guess not.
Undervolt? I undervolted my GPU as the temperature were quite high at default voltage(up to 8x.C), could that be the problem?
Catalyst/driver issues? I read from some posts that Catalyst seems to have some problem with Windows 7, does anyone have that?

It happens really random (maybe 5 mins gaming or 2hr gaming) so I don't see any pattern, the only common thing I could say is high-demand game (never occurs during normal use)

Thx for any suggestions and thx for reading the long post =)

 

[hunter315]

Did you have this issue before you undervolted your GPU? 80C at load isnt great but it isnt horrible, some hit the 90s. Return it to stock voltage and see if it works right.

Also run memtest for a few passes to confirm that your RAM isnt at fault.