Upon some testing today inside a company that uses roaming profiles, after upgrading a user’s machine with Office 2010 from Office 2003. The user’s Outlook profile updated , however when the user tried to log back into an Office 2003 box , the profile for Outlook did not load.

The only way to get this working back on a Outlook 2003 machine is to delete the Outlook profile and let it rebuild. This will work until the next time the user logs in and out of a 2010 box!

Not ideal, so would fully recommend rolling out the same version of Office throughout an organisation if they use Roaming Profiles!