microsoft outlook has accepted this meeting on behalf of

Having the same problem as these threads below:

http://community.office365.com/en-us/f/158/t/230472.aspx

http://community.office365.com/en-us/f/158/t/255913.aspx

Can't pinpoint what might have caused this to start, could be when I installed CU5 recently?

Any thoughts?

Thanks!

Update - I migrated these mailboxes from one forest to another using the Cross-Forest Mailbox Migration tool in Exchange 2013.  The messages began once the Cross-Forest Migration completed.  All the permissions migrated and worked correctly, it just looks like it is causing a problem somewhere else.