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It seems like graphic card glitch.

What Mac with what graphics card are you running and what Mac OS X version (eg. 10.4.11) is currently on it?
 
macbook

I have an old macbook 2.4 GHz intel core 2 Duo. 2 GB 667 MHz DDR2 RAM. Video Card is built in Intel GMA X3100 with 144mb vram. It is about 2 years old.
 
also

the glitches go away when I restart the computer. But after a while they came back but looked different.
 
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