Whenever I logout of xwindows, my screen goes black and stays that way. if I type shutdown -h now .. it seems to shutdown, but i can't be sure. It seems that I can still work in text based mode, but I can't see what Im doing. What could be causing this and how do I go about fixing it?

-- Yank_

Try to enter a tty console by hitting ctrl + alt + F1-F4. If this works then the system is not totally hung. This means only the X server is stuck. Sometimes you can see some output from the X server in one of the tty consoles, if so it might help in finding the problem.

Also try running this from a working tty:
# ps aux | less
and browse trough the output (use up/down arrows to see it all). Some process(es) might be in zombie state.