Some iCal users may run into a problem in which the program does not give any alerts, be them alarms or notifications for incoming invitations.
Apple Discussions poster Matt Sandford writes:
"I have Ical 3.06 on a G5 tower and for some reason i get not alerts of any sort."
Users have tried checking the notification settings in iCal, as well as remove various iCal-related preference files. However, this problem seems to be related to the calendar caches. iCal will temporarily store files in the /username/Library/Caches/com.apple.iCal/ folder, but the specific calendar cache files are kept in a different location.Fix: Remove the "Calendar Cache" files. Open the /username/Library/Calendars/ folder and remove all the files called "Calendar Cache". There may be more than one, with them all being labeled with sequential numbers. It is recommended to temporarily move these files to a safe location (such as the Desktop) instead of deleting them, so they can be easily replaced if problems arise (though being cache files these are temporary anyway and should be automatically generated and not required for the program to function).