What is the exact error you receive? Also you could try going to Run and typing in: Outlook /cleanreminders noting there is a space between outlook and the /
The exact error box message reads “The form required to view this message cannot be displayed. Contact your administrator.” This happens when I try to add an appointment/task to the calendar by either starting to type into the date box, or by double clicking on the date box to open an appointment box. I’m not using any custom forms in Outlook, just whatever came with the original program. Did I mention this is Outlook 2003?