How does iCal know the calendar where the event should be created

Hello,

I have been subscribing to meetup events for some time and was getting's too many invites and it was causing iCal to go crazy whenever I opened it. For some reason some of my subscriptions appear to be all confused.

Essentially when iCal processes the files in the Calender Incoming folder (In the Library) it never knows which calender the event should go. It then prompts on each event it processes asking me to choose a calender. As the notification does not tell me which event it is I can't even select a calender manually...

How does iCal know which events need to go into which calender? Is there some mapping file or setting somewhere..

Cheers,

Carl