Well, that shouldn't happen. What does happen is that you can't separate the Palm categories into separate calendars, so that everything appears as one calendar. This page examines the process of migrating from Palm devices to Mac:
Thanks, Roger - I agree that it shouldn't happen! But it does! In my Palm calendar, I kept things simple - almost all of the events are unfiled. When I export it as vcards and import it into iCal, many years' worth of events seem to get replicated and appear on all kinds of crazy and irrelevant dates.
Other people have complained about this behavior as well - I've seen it in a number of posts.
Do you know a workaround?