Computer Freezing

[curtcheese64]

Whenever I play HL2 or a variant of the game such as CSS my computer will freeze after about 15 minutes of play. Windows will sometimes give a hungapp error. I have an opteron 146 overclocked to 2.6ghz on stock cooling but it's prime stable for 27 hours. My cpu and gpu temps seem to be ok. What could be the problem?

BTW here are my system specs:

DFI Lanparty Ut NF4
Opteron 146 @ 2.6ghz (stock cooling)
1gb pc4000 OCZ Vu Gold
Connect 3d X800 gto PCI-E (Unlocked to 16 pipes)
550 Watt Enermax PSU

 

[reggie_da_man]

Well what are your temps?

 

[curtcheese64]

CPU temp while running 100% load on Prime95 maxes at 50-51C. GPU temp while finding max core in ATI Tool was 70-71C with stock cooler at 100%.