We had a client who’s To-Do bar showed “The operation failed. An object could not be found” and their reminders would stop working. We could get it working again by deleting the Outlook Profile and re-creating it, but a couple of days later the problem would re-appear. We tried hacking the registry, deleting LocalAppData and AppData for Outlook all to no avail.
Then we found a post that led us to Exchange 2010 SP1: Database Integrity checking, anyone who’s been around a while will be thinking “I can’t afford to take the database offline for an ISINTEG”, well the good news is you don’t have to anymore.
I ran the following EMS command and it solved my To-Do bar issue
New-MailboxRepairRequest -Mailbox User -CorruptionType FolderView -Verbose