Hello everyone. Anybody any clue to this (or must I live with the fact). Because of suspected data corruption in one of my GW user accounts, I had to recreate the account using the existing FID (TID: https://www.novell.com/support/kb/doc.php?id=7014868). Of course, I previously archived everything before deleting the old account, deleted old account, created new account (following TID) and un-archived after that. Mailbox thus recreated is running fine, all data preserved.

However, I found out that appointments that were created by the OLD (deleted) user account (and of course visible in the newly created one) cannot be modified any more. That is to say: user can open the old appointment, make change to the appointment and post the appointment. But the user will immediately receive an "appointment refused" from the recepient.