Beware of running multiple versions of Outlook in you enterprise Exchange environment especially with roaming profiles. There is a known issue when a user who normally uses Outlook 2007 to access their email account, then accesses that same email profile logged into a machine that is running Outlook 2010. By accessing it with Outlook 2010, the messaging service is updated to the Outlook 2010 variety and then when the user attempts to open their Outlook email profile again on version 2007, they will receive the “You have a previous version of the Microsoft Exchange Messaging Service. Create a new profile.”
The easiest way around this is to go to Control panel and “Mail” and delete the profile that was accessed using Outlook 2010. Readd the profile or let Autodiscover set this up again using Outlook 2007 and you will be back in business. For most the solution may be to advise enterprise users who have not yet received Office 2010 to simply use OWA to access their email when away from the office workstation which has Office 2007 loaded.