After starting the computer and searching in spotlight, I get this weird graphics glitch on the screen. It only does this once; if I open spotlight again it's gone. It happens again though if I restart the computer. Has anyone else experienced this problem? Is it more likely to be a software problem or hardware problem? Some apps do this too. For example, sometimes when opening large powerpoint files, the progress status bar shown while the file opens has this same pixelated effect.