A search didn't seem to yield another post covering the same issue. Recently, I've had a weird problem on my 14" display. Irregularly, the screen will display squares of red/green and brown over whatever application I am using. These squares, about 1 square centimeter, will go away if I run my mouse over them. Sometimes, it gets really bad: 50% of the screen surface area will be covered in these squares: if I move or resize a window of an application, the entire area of where the window used to be is covered in them. But this isn't the only action that triggers it: even typing in a Pages or word document sometimes the most recent test becomes blocked by these square blotches - but they go away if I run the mouse over them. The only correlation I can make to behavior and the appearance of these squares is when my computer has been on for a 2 hours or more. But when restarting, it happens again. Any application that I use (safari, firefox, iphoto, word, pages, etc) can trigger it, as can Finder. I'd say that the more apps I have open, the more likely it is to occur, but it does occur with only 1 application open as well. I've tried reinstalling Mac OS X - same problem. It will sometimes go a week without happening, and then a couple days when the computer is so annoying as to be unusable. When I took it into an apple store, I couldn't replicate the problem. My laptop is 1.5 yrs old and I have applecare. Does this sound like a hardware issue: perhaps with the graphics card? Any suggestions would be helpful: I could call Apple with a more specific description in hopes they could fix it. Thanks!