Black double curser lines on screen

When I am watching Tv with Media center there are no black lines on screen it is perfect

I have played with so many things i am finding thing i never new i had Thanks for the help its like I drew a pattern on the desktop some are minus signs some are equals and some are equals with a dot to the right of the longer line now at times sometimes the whole screen is filled with the 5 columns and you click the mouse left click and they go away.

Check inside the case for a stopped fan....blow out everything while your there.....

Thanks good idea been there did that reseated the card etc checked ram then reseated that also checked other cards. I almost had my self convinced that some one is remotely doing this but the way they blink and the randomness of the black lines i said i's good but nobody is that good. Plus i am behind a router and Symantec End Point protection 11.5 with the firewall on to ask if anything tries to access the system.

What card did you order?

SAPPHIRE HD 6770 Vapor-X from Newegg

Guess if its not the card, i can always put the card in this system my media center which has the identical card and run two 5670's in the media center and i will have an excuse to build a new system with an i3 5 or7 cpu and the newest chipset, had to get permission from boss (wife) to order the card which she agreeded have to fix the problem or use the GPU for a clients system some time in the future.

So far no black lines today which makes me think it could be the vram deal like someone said on another Forum. The same thing happens when you have system memory bad sometimes it acts up others it doesn't, so is that the case her, but its the memory on the video card. Even check power supply voltages.

Well the HD5670 is off to Athlon Micro for RMA marked the card and took pics of it so i can see what i get back or if they find anything wrong with it, but the new Hd6770 Vapor X is a keeper and have got a free copy to Dirt 3 not that I play that many games, but with heavy load on GPU has got up to 46c so far. When I get the other card back might do the dual set up on my other Media center system which has the identical card. Thanks for every ones help.