Outlook Hanging on Exit

I have a client using Outlook 2000 w/Office 2K SP3. Sometimes when exiting Outlook, it exits instantly. But occassionally it will hang with the message “Please Wait While Outlook Exits”. The only way to get rid of it is to End Task. He is running XP Prof. with current updates and service packs. It used to do the same thing under XP Home Edition.

Any Ideas?

Brian