A client, with lots of events in her iCal, created a new reoccuring event. It worked fine in iCal but showed up everyday on her iPod. Deleting and recreating the event did not help. Either did resetting the iPod.
Apple suggested she reset the sync history. That didn't work. Then they suggested she delete the entire calendar and start over. That was not a good solution since her calendar has so many events.
I solved the problem by backing up her iCal data, deleting the calendar in iCal, and then manually dragging all but the troublesome event back onto iCal.