Booting / Graphic Problem
I have this iMac. It doesn't boot properly: Sometimes it works for a while but then it crashes. After a crash (complete freeze) it doens't boot properly: I have a blank screen with the pointer only and arount the pointer there's some graphical "noise".
After the initial problem I tried and got the system to boot in SAFE MODE. I copied all the files I needed and formatted the drive, reinstalled OSX 10.8.3. Worked fine for a while, same problem now (Just to know: I didn't copy the personal files to make sure the problem wasn't related).
Since the crashes happen after some use and the iMac seems to be very "used" I'm going to disassembly it and clean the interior (suppose is a overheating problem).
Just wanted to know if it is a common problem and if it's related to special components I have to swap (could be GPU?)
Not to worry most systems don't have warranty coverage, unless Apple has acknowledged they had a problem that they will service for free. I don't know of any extended warranties on this system related to the video.
In this case yes, replacing the logic board out is a viable solution here. Since you've already taken a dip into the deep end you shouldn't have any problems. Just make sure to follow proper ESD practices in the process.
If you got some extra cash see if you can boost your CPU speed on the replacement logic board. Just make sure it's compatible with your given system (maybe going up to an Intel i7).