15'' PowerBook G4 won't boot when "warm"

[fnkyrbt]

Hi, sometimes my 15'' 1.6 GHz PowerBook G4 won't boot. I can hear the standard boot sound, the hard drive spins up, but the screen stays black. This always seems to happen when I reboot while the powerbook is still warm. When I wait for an hour and it cooled down, the system will usually boot.

Resetting the bios memory didn't help. Could this be a temperature sensor problem? Is there a way check if that is really the case?

Thanks...