black screen after logout...

hi,

after loging in and doing my stuff on the gnome desktop which seems to be normal other than gstreamer plugins are reported as not present when i have reason to believe that they are. and then loging out i get a black screen.

the only way i know how to get out of the black screen is to hold the power button until the unit shuts off, reboot to get back to the login screen.

the text based login prompt is briefly displayed before the screen goes black.

please advise.

What is the video chip?

this is on an apple ibook ppc.

i believe it is ati radeon ly.