Two quick suggestions:
a) start Mathematica in a terminal window with the -clean option,
mathematica -clean &
This resets initialization files in case one was damaged or has incorrect/out-of-date data.
b) In case of a video driver incompatibility, try
mathematica -mesa &
to use software rendering methods instead of hardware (video card) acceleration.
The option -defaultvisual sometimes helps, too.
Does the Mathematica 9 Kernel ("math" script) work? This is a plain-text interface.
refs:
http://support.wolfram.com/kb/3274http://support.wolfram.com/kb/3303
