Random Lockups

I just got a new eVGA 6600GT video card for my system (specs below). All has been working well but recently it has decided to randomly lockup. When it locks up it eithor just makes my monitor screen go black (but the video signal doesn't die) and I cannot do anything OR just recently it just locks up and my mouse pointer gets all artifacty (if that is a word) -- I don't think it is my PSU, it has a lot of power in it. Maybe a bios setting? Drivers? I updated my AGP drivers and I have the latest nvidia drivers. Running out of ideas and it is annoying just to have it randomly lock up when I am surfing the web / playing a game.



Spec

What card did you have before? I've heard of problems upgrading between brands...Also...How old is your monitor?

card was a Gainward gf4 ti4600. Monitor is getting old but is 21inch and still haven't seen a need to upgrade it yet.