This was an interesting problem and took some time to solve….
In the past, i.e. pre-10.4 (tiger), iCal used to handle this fairly well, however, under 10.4 there have been a few weird crashes and after one such crash iCal would not restart. However, a solution was found…
- Removed all calendars – didn’t fix it
- Removed all iCal preferences – didn’t fix it
Switched to another user account and iCal worked fine….. This suggested the problem was specific to the first user account…. So, what was left? Preferences were gone, the calendars were gone…. However, one thing was clear, there was clearly something in the ‘broken’ account that iCal was using as a) the program kept crashing and b) when iCal started the window would come up (briefly) but not in a default screen position, which it should do after removing the preference files.
After some more digging it turns out iCal now creates a folder called ‘/Users/XXX/Library/Caches/com.apple.iCal/’, where XXX = the user name. This folder contains three folders: inbox.calendar, Incoming and ‘Temporary files’. I am not to sure what these folders / files do but deleting the ‘com.apple.iCal’ folder (after making a back-up copy just incase) solved the problem.