I think that my video ram is corrupted. Often in firefox I have squares of random pixels which appear only when hardware acceleration is enabled. They look like this: When scrolling them out of the screen and returning to the same spot they disappear. Sometimes it also happens in the window of other programs, buth only very often, and then it's a rectangular. I've only seen a rectangular once but I think (as far as my feeling is correct) that the surface is the same size as the squares (I mean the same ammount of pixels is broken). 1 weird thing, today I tried RescueFox which is a preview of a new mozilla browser game engine in firefox. Although hardware accell. is off it did show a very long stretched rectangular. Maybe this is because the game forces hardware accell? But here the rectangular also moved together with the camera movements and actually acted like a usual game texture. Memtest doesn't find anything wrong with my RAM. The intel cpu diagnostics tool didn't find anything wrong with the cpu either. The artifacts don't look like a GPU error, so this leads me to the conclusion that it might be the video RAM. Now it can be either the RAM of my nvidia or the one that's used by the i5 graphics. The intel diagnostics tool also tested the i5 GPU by revolving a 3d cube and it passed the test, but I don't know if it tested memory too. I doubt that it's an issue with the nvidia 'cause scrolling in a simple forum like MDL shouldn't trigger the nvidia to go on. Any ideas of what might be wrong? Or does anyone know what memory is used by the i5 GPU? EDIT: What I forgot to say is that there can be multiple squares in 1 Firefox window, it's not restricted to 1 displayed square at a time.