Ibook Rage M7 Black Screen An Cd-rom Error


after searching many sources and websites, maybe somebody here can help. it would be great, thanks.

i have a white ibook double usb/firewire/800Mhz/RageM7/vram 32mb and do experience strange blackscreen-problems. sceen goes to sleep after opening the ibook and after it was in the sleep mode (never sure if it really slept then). this happens sometimes and I can solve that problem by restarting or closing and waiting to see it go sleep, (indicated by the pulsing light). after 2 minutes it wakes up properly.
what always happens in the sleep modus is that the CD-Rom searches for a CD and gives every minute that spinning sound, up and down as if a CD was inserted. Not a problem while working.
the ibook comes with cd-rom scr-242, and mac osx 10.2.3
firmeware has not to be updated I think, the dealer says it does not go with the apple replacement program (defective motherboard/inverter)

so please, any idea would be helpful,
thanks, sven