I recently got an EVGA 8800 GTS 512 to go with my new SAmsung 40" 1080p monitor. When I first got it I was just running my monitor at like 1280x720, and it looked ok. I wanted to run it at Native, so I changed the output to 1080p HDTV. Now all my games are freezing, my PC totally locks up and I have to hard boot it. My graphics look amazing, when my PC isnt freezing up. I havent done any overclocking to the videocard whatsoever, I usually run the fan at 80% to eliminate any heating problems, though the card itself does get quite warm. 

Idle my videocard runs at about 39c, my ambient temps in the case are around 37c, and my processor never goes above 43c under load. Ive run memtest for 7 hours with no problems, just to knock out the problem being with memory. This really has me aggrovated though, because I cant play anything, or watch any videos or listen to any music without my PC randomly freezing up. At first I thought it may be a power issue, so I did alittle overclocking of my CPU and memory, and put it under 3dmark for a while, it ran for about an hour, than froze. Im really at the end I dont know what else to do. I even tried taking the soundcard out to see if it was that.. 

What is the GPU's temperature at load, when you are in a game or 3Dmark for a while? 

The card only goes up to about 55c under load. I have really good cooling in my case.  

 With overclocking your always taking a risk even if your temps are fine, in theory your putting more strain on a part which comes with default setting so there may of been a chance or something burning out or something along the way being effected,

Try and run a few diagnostics:

- Spyware and virus scan
- HDD check
- Display drivers
- Mobo drivers
- All other drivers

I presume the monitor can run on 1080p?

I forgot to repost. I fixed the problem, all I had to do was reseat the videocard... who would have known o.0