BSoD running games--stable otherwise

Hello, all. I'm currently dual-booting XP and Vista Home Premium, and I'm having an odd problem with running games on the latter.

I've got an Athlon X2 4800 CPU with a Radeon X1800 XL and 2GB of PC3200 RAM on my PC, and I was immensely surprised at how well games ran on Vista--after I tested for about ten minutes. However, after playing for a longer period of time (no matter which game I was playing, and in one case while merely watching a Flash movie), everything locked up, and the screen went to--you guessed it--a blue screen of death, complete with Microsoft's famous vague "critical stop error" message and indecipherable numbers to show the location of the error. This happened at random points, and not when the CPU or graphics card load was significantly increased relative to the environment it was performing in (i.e. it happened at a random, relatively calm moment in Oblivion instead of a spell-flinging frenzy). I've got the latest drivers for everything, so far as I know (save my G15 keyboard and Copperhead mouse, which there are no Vista drivers for yet).

I'm not sure, but it's possible that Vista has gone to a BSoD when idling, as I once found it had inexplicably restarted after I left it running for a while.

Any ideas what might be going on?

Hiya, thanks for responding. I installed the Dual-Core Optimizer (I already had it on XP, but wasn't sure if I needed it for Vista as well.)

Before I run a first test, though, I'll report my findings in other areas.

No Starforce found...thankfully. I hate StarForce.

This was a quasi-clean install. It was a fresh install on the second hard drive of my system--the other HD is still running XP, and both OSs have access to non-protected files on the other's hard drive. (Kinda cool, actually.) However, of course, I'm only running games in Vista from the Vista hard drive.

Not sure about "services", but I generally have ~50 processes running in the Task Manager. Most of these are Windows's normal assortment of stuff, and the rest is either related to ATi and the Catalyst center, OpenOffice, or my G15.

I'll be running a test now (read: playing Oblivion until either I crash or it crashes), so I'll give results later.