Comment 57 for bug 22976

The Jaunty PowerPC live CD has recently been updated. Can you please try it? http://cdimage.ubuntu.com/ports/daily-live/current/

General instructions for debugging "black screen" issues from a live CD:

Please try a Jaunty live CD: http://cdimage.ubuntu.com/releases/jaunty/

At the CD boot menu, add "text" to the boot options:
https://help.ubuntu.com/community/BootParameters

The CD will now boot but not start X. At the text prompt, enter this command:
 xinit -e 'sh -c "xrandr --verbose > xrandr.log" '
This will try to start X and log some information about the active screen resolution to the file xrandr.log before it stops X again. Copy the corresponding X log to the current directory:
 cp /var/log/Xorg.0.log .

Now edit xorg.conf to make X use the "vesa" (failsafe) driver:
 nano /etc/X11/xorg.conf
and change the Device section to look like this:

Section "Device"
       Identifier "Configured Video Device"
       Driver "vesa"
EndSection

Then start X which should give you a desktop session, although with low resolution:
 startx

>From here, attach the xrandr.log and Xorg.0.log (which are in the Home
Folder) to this bug report. If for some reason you can not log into
launchpad from the live CD (network problems etc), you can also copy the
files to a USB drive now and attach them from another computer or
session later.

See also https://wiki.ubuntu.com/X/Troubleshooting/BlankScreen