so just to be clear this isn't a system issue i will give a list of my hardware
intel core i5 750 running at 3.3 ghz cpu
gigabyte GA-P55M-UD2 motherboard
4gb corsair dominator xms3 1600 mhz ram
Nvidia gts 250 1gb
450 corsair psu
liquid cooling with 120mm radiator
so, my computer is a custom built one from ibuypower and i've run into some trouble with it, when i boot it up and start to play a game, the framerate is excellent(nfs shift at over 90 fps), but for some reason, after about 20 minutes of gameplay, the game crashes and when i restart it, the game now runs at 12 fps. WTF
i haven't got too many computer games but to be sure i went on cod mw2 to try as well and its the same issue, around 120 fps on a normal day but it just laggs to 20 after turning the computer on for more than 20 minutes.
i have no idea how this happened, still tweaking around the bios looking for an answer, would be great if you guys could help!
so when you reboot it automaticlly underclockes your card, that sounds like an overclocking software issue? maby you should check all your softwares for overclocking, maby you should uninstall and reinstall you drivers.