Just thought i'd add my two cents in. I've been having the exact same problem (same new 2004 ibook), when I start X I get blinking horizontal lines and then when I try and kill the xserver the whole ibook locks up.
I'm using vanilla 2.6.6 kernel confiuged according to instructions in: http://seb.france.free.fr/linux/ibookG4/iBookG4-howto.html One thing I have noticed though, a couple times I haven't configured my krenel properly to allow for radeonfb to work..consequently when I booted up the screen faded to black almost immediately. I noticed that the computer was still booting so I waiting for the hd activity to stop then I logged in blindly and loaded up X. After a couple seconds, I could very faintly see KDE starting, the spaslsh screen followed by the default desktop. Don't knwo if this helps, but I figure it points to the problem being with the framebuffer... cheers Andrew
