Sleep mode broken by empty CD drive

This malfunction is not given when power is offline.
Martin Trautmann wrote on :

Hi all,

my iBook G4 shows a strange behavior recently: When plugged in, lid closed (which should force a sleep) it does restart every 10 seconds for a fraction of a second. It sounds as if it does want to read from the empty CD drive. The background illu turns on (the apple on the cover of the iBook bekomes visible) and turns off again.

This malfunction is not given when power is offline.

I installed both Quicktime 7 and security update 2005-08 recently on MacOS 10.3.9

Any idea what went wrong? Where can I monitor which application does cause the wake up?

Thanks, Martin