One of the two users with this problem had an entry under 'Generic Credentials' relating to outlook, I have deleted this entry and asked him to keep...
I'm giving HAP a go, the installation instructions are pretty out of date though so having trouble setting it up in ISS, the latest tutorial doesn't...
Either license it as your mandatory profile user and close it back up or find out where it's storing the license registration and distribute this to...
I would do as Sukh says and create a new database to move the mailboxes into as this will eliminate the white space. One thing to bear in mind though...