[iBook] Problem with alarms

[Christophe Claude]

Hi iList,

I am a new apple user (3 months) on a iBook G4.  I used the iCal's
function alarms to get out the computer asleep and to launch a song
via iTunes to inform me of one event;  what functioned pretty well. 
For several days, OSX has obstinately refused to get out of sleep for
launching iTunes and on the other hand when I double click to wake up
the iBook, iTunes launches whereas the hour that I had wished for
alarm is for a long time exceeded.  I removed the preferences of iCal
(.plist) and started again the application and even started again the
computer but that does not change anything,
Thanks for any advice,
 Chris