Serious graphical artifacts

[Carborundum]

As per the thread title, I sometimes experience rather significant visual artifacts in Maverick. Some programs are more affected than others, but the problem is systemwide. It's most obvious when trying to read a pdf-file, as you can see in the attachments.
Interestingly, video never seems to be affected; even when the artifacts are so bad I can barely see what I'm doing, watching a movie in VLC works without problem (although the VLC GUI itself is affected).

The problem doesn't appear every session, but it is common. Approximately every third session is affected, and once the artifacts appear they remain until I restart the computer.

So, what might be causing this, and is there anything I can do about it?

[linuxuser12345]

Maybe some files are corrupt? Try running a LiveCD and see if it happens in there. You might just need to install the proper driver for your graphics card. Go to "System", "Administration", "Additional Drivers"

[linuxuser12345]

I had a similar problem once. Thought I couldn't fix it but got there in the end after some trial and error.
I'll see if I can find the link.

EDIT: Got it: here - http://bit.ly/g3je8t

Next time, use www.tinyurl.com for shortening links. Tinyurl doesn't have huge, flamboyant advertisements.