Now that Office 2010 has RTM’ed, we’ve started to see a number of issues pop up where customers are finding that they are having problems reserving a conference room using it. The reason is that Outlook 2010 by default has Direct Booking disabled. This is by design since Direct Booking is the old Exchange 2003 way of doing things and Exchange 2007 and 2010 has automatic processing of resource mailboxes.
If you are still on Exchange 2003, however, you may have the need to enable Direct Booking for your clients. In order to enable it in Outlook 2010 you will need to add the following DWord in the registry for the organizers client:
Hope that helps some people out.