Exchange 2k Public Folder Permission issue

Running native multi-server EE Exchange 2000 SP3 w/ Outlook 2000 clients. Some users unable to create new items (subfolders) under particular Public Folders even though they are listed as the owner of the parent folder. Some users tried to reserve or modify calendar items w/in public folders and get error messages stating that either the conference room folder has been deleted (which it hasn’t) or user does not have permission to reserve the room (which they supposedly do according to their permissions).

“Unable to create the folder. You do not have sufficient permission to perform this operation on this object. See the folder contact or your system administrator.”

All folder owner permissions appear correct, but still having intermittent issue like described above.

Any ideas on what could be causing this and how to correct it. Thanks.