System becomes unstable after memory-intensive apps

[Snell]

It seems like the more RAM I use, the more quickly I'm forced to reboot.

 

If I run only conservative apps--Mail, Safari and maybe an audio player--my machine will stay stable for a couple days. However when I load anything that requires a lot of RAM, WoW especially, my machine will become unstable after ~40 minutes.

 

By unstable I mean that apps start crashing, sometimes the mouse starts lagging, eventually everything closes unexpectedly, and Leopard resets itself without rebooting: my startup apps load and I get a warning about ext2 (which I get after a full reboot). If Leopard doesn't reset itself I have to reboot manually in order to regain stability.

 

I'm running Zephyroth 10.5.2

M2N-SLI Deluxe

5600+ X2 Dual Core

2GB Ram

 

I don't know if additional information would help. Could this be a problem with my hardware? Maybe I should try reinstalling?