OS 10.4 - macbook auto restarts after certain amount of time

help please, this is killing me.

ever since i re-installed parallels (windows xp), my macbook puts up a prompt asking whether i would like to restart my computer or not. if i dont choose 'cancel' it automatically restarts.

i have a screensaver set 'on' and i don't see anything within 'power saver' or 'display' that would cause this behaviour.

any help is much appreciated.

mags