why does ical forget recurring events?

I've got a weird situation happening. I have my work schedule set up as recurring events. Every Monday repeats on Mondays, Tuesdays on Tuesdays, etc. (its not setup as a M-F repeating event). I title the event as "Work" and then on a daily basis, I enter the store location for my scheduled shift (I work a merchandising job at a different store every day).

The problem is that iCal is forgetting past events; they don't show up on my calendar anymore. They've simply disappeared. But only my recurring work events. Not anything else. And it's not even consistent in how it forgets. Some weeks its all my "Work" events. Other weeks, Wednesday will still be there, but the other days are gone.

I've been using iCal for a couple years between my iPhone 4 and my MacBook Pro. It doesn't make sense to me why it would be doing this. Any help would be appreciated.

bryan