A number of MacBook users have been experiencing a problem in OS X where the system shows areas of graphics corruption around windows. The corruption appears to be a black area of blocky lines in no particular pattern, and seems to be in the area of the window's shaded region, moving with the window when it is moved.
This behavior seems to be specific for computers that are running Intel GMA X3100 graphics chipsets. It started occurring with OS X 10.6 for some people, though for others the 10.6.1 update spurred the problem, and as of the latest 10.6.2 release this problem has not been addressed. The problem seems to happen most when multimedia files are being played, especially with beta versions of Adobe flash are being used. From the description and screenshots of the problem, this is clearly a problem with the GMA graphics drivers in Snow Leopard, so unfortunately a true fix will have to come from an update from Apple.
Recent reports suggest Apple is working on significantly improving support for more OpenGL 3.0 functions and extensions in OS X 10.6.3, which implies Apple will be updating the graphics drivers in the next update. Hopefully the bug that is causing this problem will be addressed then, but in the mean time you can try the following to hopefully clear the problem or pinpoint faulty settings:
- Reset PRAM and SMC
- Boot into safe mode and clear caches with OnyX or other maintenance utility
- Try a different user account
- Try different graphics settings (bit depth, resolution)
Overall this glitch will not hurt anything, and just affects Apple's rendering of window shadows. The window contents are still visible and can be interacted with normally. While it is unsightly, if you can bare with it hopefully Apple will address it soon. Some people may consider reinstalling OS X to tackle this issue, but those who have done this have not been able to clear the problem.