Here it was a matter of Active Sync, Windows Mobile Device Center (WMDC) and it's connections to from said servers. WMDC doesn't seem to care if I connect WM 2003 to WM 6.1. It all works.
Our 6.5 devices are not in house yet. Sorry.
Does anyone know if Outlook 2007 Business Contact Manager works with Windows Mobile 6.5? The BCM web site only lists up to 6.1 Thanks