For many (5) years, my company has had a custom form that accepts meeting
requests, is emailed to a calendar administrator, and then if approved, the
appointment item (generated by vbscript from the form) is moved/copied into
the public folder calendar.

At the beginning of this past month (February), we are suddenly getting a
"Can not copy the items.  Cannot complete the copy operation. The items may
have been moved or deleted, or you may not have sufficient permission."
messages.

Permissions are all correct on the calendar in the public folder (Owner).  
Any ideas as to what may have happened?