I got a new gigabyte 450 video card a few weeks ago as an upgrade to my ancient 8800gs. I didn't change anything else out of my desktop (AMD Phenom II X4 955 processor, 4 gigs DDR3 RAM), but now my computer locks up during some games under load (but not all). For example, Empire Total War and Mafia II freeze after ~15-20 minutes of playing (total lock up, can't alt tab/cntrl alt delete). Mass Effect 2 is totally fine, as is Mafia I for as long as I want to play. I checked the temps on the GPU and CPU, they were both below 70 the entire time so I don't think that is the issue, more specifically around 50 at rest for the CPU and low 60s under stress. I made sure to update to the newest drivers with no avail (full uninstall/reinstall), I even disabled my sound drivers as a test but the game still froze, so I'm fairly certain its related to the card somehow. Anyone have additional ideas as to what I can test? Running windows 7 64 bit.