I had a problem with a migrated user from Exchange 2003 to Exchange 2007 not showing the correct version number. It was not listed as Legacy Mailbox and it resided on a Exchange 2007 store. Running the get-mailbox command I saw that the version number on the mailbox was 0.0 and not 0.1 for Exchange 2007. Because of the mailbox being in this state the user could not connect to OWA. I got the following message:

Inner Exception
Exception type: Microsoft.Exchange.Data.Directory.InvalidADObjectOperationException
Exception message: Property Languages cannot be set on this object because it requires the object to have version 0.1 (8.0.535.0) or later.
Current version of the object is 0.0 (6.5.6500.0).

To resolve this problem you need to correct the properties of the mailbox. Do this by running  the following commandlet  in Exchange Management Shell:

Set-Mailbox -Identity <user> -ApplyMandatoryProperties

View KB 931747 article over at Microsoft Support, http://support.microsoft.com/kb/931747