It's the graphics card drivers! Aaaaalways the drivers!!! :D
I get such a nice little message that tells me when there are new versions of my drivers available at the official website, so my drivers are always actual. Most people I know, use Linux (openSuSE) too.
PS. I'm typing this on Ubuntu, out of free will. (That would be the same if a die-hard Mac fain said: ps I'm typing this on Windows Vista, out of free will)
My programs do never have bugs. Instead, they have unwanted/unexpected features.
My programs on the other hand are all interesting bugs that behave in a quasi-orderly manner... So I blame the uncertainty principle when they actually work as (un)expected.