I upgraded to a new Exchange 2010 server on a new machine. Had an old Exhange 2007 server running which is DC. Transfered all the mailboxes etc. to new Exch 2010. Everything worked fine on new server until I uninstalled Exch 2007 on the old server. Followed the technets for "Completely Removing Exchange 2007 from a Server". Now some (not all) Outlook 2007 clients ask to login. After login everything works. The old exhange 2007 continues to be the DC.
Where should I start for fixing this?