The solution here worked for me too on a G4 with Debian Wheezy and the Xfce desktop. I'm adding this because I had endless problems with the screen resolution being stuck 800x600 on a Packard Bell Viseo 230.
Having been through just about every possibility (or so I thought) with wrong advice about xrandr and what to put in the conf file, this is the solution that actually worked.
Thankyou to linuxopjemac for:
sudo mv xorg.conf /etc/X11/xorg.conf
Now, if only I could get this thing to recognise the Norwegian keyboard layout...
Thankyou Ubuntu forums!
This is not a reply but a plead for help. I migrated from 12.04 to 12.10 (IMac G5 PPC, NVIDIA Geoforce FX5200 graphics card), after the update I cannot see any text or logos on my display. However, the wallpaper (a family photo) displays as it was with 12.04.
I am assuming is that is the Xorg file, but how can I edit the file if I cannot see what I'm typing?