Appointment Scheduling Problem

[Bartly]

In Calendar Appointment Scheduling, Adding names to the Attendee List no
longer works, the names are not recognized (do not underline). The names have
to be added via Add Others.

This has happened to a couple people on our network, not all. They are in
Outlook XP. We use Exchange 2003. Windows 2003 domain.

Any ideas to correct this?

Thanks