I installed Xubuntu 8.10 on my iMac G3, though this time to take up the entire hard drive. After I finished the lengthy install and rebooted, I got the normal bootstrap+yaboot routine, but then heard the CRT turn off and the power LED started dimming in regular intervals (Not smooth like the sleep LED). When the light dims, I also hear a sort of ticking.

I can boot from any disk fine and copy files / format the hard drive with no problems.