I recently revived an old Powerbook G3 Pismo (the one with the firewire ports) and decided to install ubuntu on it to play around and check it out. After installation Ubuntu would not properly start - I got a series of messages about GNOME not being able to start, Nautilus aborting and a third which I forget. It turns out that Ubuntu won't start up if there is no date in the computer. My PRAM battery had died and I had found a new one - but the date still hadn't been set. The problem was solved by logging into a terminal session and setting the date - bingo, everything works fine. Just thought this might be helpful to somebody - it stopped me in my tracks for a while.