Problem......graphics card?

[Mc55m]

Okay so i built what should be a nice little system for game....

GA-MA770T-UD3P motherboard
Phenom II x4 955 black edition
Asus DirectCu 5850
8Gb DDR3 OCZ RAM (4 sticks of 2Gb)
Antec 850W PSU
3 SATA HDDs 40gb, 250gb and a 1tb
Windows 7 64bit

now, heres my problem, it started with everytime i would try to push the system with a game thats got some decent graphics(COD4, SCII beta, even TitanQuest and now even Civ 4) the screen would flicker a bit then get vertical lines and lock up.....I checked the drivers, uninstalled and reinstalled a couple times to be sure, but is not that. I think theres something wrong with the card, but i want to be sure before i go to Asus to get the card replaced(i passed the 30 days from newegg cuz i lost my job and gave up on trying to game/fix the problem so i could game for a couple weeks). When i first built the system i had a bad stick of RAM and got that replaced. So by then i was already almost 2 weeks into that 30 days so that didnt help......digress....anyway I have gone through so many thing trying to figure out the problem, GPU-Z, 3D Mark, etc, The system crashes when i try to use 3D Mark, i get the lines and it locks up.

any ideas would be awesome!!!

 

[dr.stevil]

I'm pretty sure that this is a common problem with the 5000 series AMD cards.

Not sure what the resolution is, but I've seen it brought up before. Try searching the forums or google.

 

[TGA]

Well you might want to pull 2 sticks of ram and see if your still have problems.

Some people experience issues with 4 sticks that can require a little tweaking to get things stable.