The form required to view your message cannot be displayed.

When trying to create a new calendar entry one of my users is receiving the
message "the form required to view this message cannot be displayed please
contact your administrator".  Existing calendar entries can be opened, you
just can't create a new one.


Deleting frmcache.dat and restarting outlook

Or

Disable plug-in that uses the Outlook form one at a time to see if you can create new calendar entry. (Meeting Place being one of them)