can't cancel iCal subscriptions

Every time I open iCal I get numerous alerts about meetings that I subscribed to at a previous job. I cannot figure out how to make the alerts or the synchornization stop. I must click off on at least 20 dialog boxes from iCal asking what calendar to add the events to.

I no longer work at the job; the team I was on at the company doesn't even exist anymore(!) and hasn't for over a year. These alerts make iCal completely unusable.

I have deleted the calendar listed under 'subscriptions' but each time I open iCal it comes back.

Can someone tell me how to make them stop?!