Hello, So I built a new computer a few days ago, athlon x2 6000, 2 gigs corsair xms2 ram and ofcourse the powercolor HD4850 512mb. The first thing I did when I got the card back home and started putting everything together was to take the heatsink off, clean all the grease that was already on there off (with isopropyl alcohol) and apply some Arctic Silver 5, which I did properly and carefully. Put the computer together, everything worked fine except for a few wierd things i noticed on the screen at some point when I started the computer up, blue squares over the screen. This went away and I thought nothing more of it. A few days later I started my computer and there was just crap all over the screen; lines running down.. the bios text would be replaced by pink blocks, i would let the computer start up and the screen would keep going black then coming back with a different set of graphical anomolies.. little blocks, etc. I just assumed at this point that the card was ****ed, however, a few restarts later, everything went back to normal (the computer started off the same, with the pink blocks but then the screen went black and came back fine). I played games and it was fine, i ran 3dmark06 and got good results.. so the card is obvoiusly fine. It is definately the card too, because i tested it in my brothers computer and same thing happened. Then upon restarting the computer it went back to the way it was before, and i would have to restart it/turn it on /off many times before i could get it normal again. I initially thought that I could have got some AS5 on something and it was causing a short circuit or something, but I thoroughly looked over both sides of the card and around the gpu and it is immaculate, everything is perfectly clean and in order. Im going to take it back for warranty tomorrow but i have a feeling I'll be waiting a while before I see another one, so if I can avoid this I would rather. Anyone ever seen anything like this before / got any ideas? Thanks, Adam. PS. Should have mentioned that it is not a heating issue because I monitored the temperatures and they are perfectly acceptable.