I am also receiving this error when I try to connect from one workstation. I have six other workstations that are connecting successfully. The workstatoin in questions is running XP Pro with Windows Messenger 5.0 installed. This one workstation (no others) was also running MSN messinger (latest) with a .NET passport. I installed the Window Messenger that came with the Exchange 2000 disk (ver 2.2) and the other workstations used it fine (all XP Pro). This one workstation give the above error even after downloading and installing Wnidows Messenger 5.0 for Exchange 2000 and XP. I'm at a loss.... HELP. I am getting numb from reinstalling...
David