Stats:
I have an iMac G4 17" (the style that looks like a lamp where the screen rotates).

My problem:
My computer seems to signoff completely if it is idle for too long. No screensaver or anything, the screen goes black (which i think is the powersave) then a few minutes later it will log out completely to the login screen. It never used to do this and I'm not sure why it started.

Does anyone know of a setting or something that I might have accidently changed ?

Any information would be helpful. Thanks