... after trying all the things mentioned here and in the web, i've got the solution..
Two weeks ago I deleted a user in the AD. The Exchange mailbox of this user still persists disconnected for a default of 30 days and can be seen in Exchange System Manager marked with a tiny red symbol. So far so good... Yesterday I ran a DB defragmentation using eseutil with the /d option. Obviously, this disconnected mailbox lead to a DB access problem for BackupExec. My very last try was to purge this mailbox in System Manager - and after that the misleading BackupExec error message was gone...
What do we learn? After running a DB defragmentation with eseutil we have to manually delete disconnected mailboxes before BackupExec can backup that Information Store...
Hey folks from Microsoft and Veritas, you should publish a KB/Technote article about that...
Bye,
Wolfgang