opening other user's mail box when Outlook starts...

Hi,
It seems like last week I was able to configure numerous Outlook clients to open other users' mailboxes when Outlook starts (Outlook XP). Today, when I try to configure one of the secretary's Outlook client to open her boss's mailbox when Outlook starts (click on the Outlook iconPropertiesE-mail accountsView or change existing e-mail accountsChangeMore settingsAdvanced tab) I get an error message stating "The name could not be resolved. The action could not be completed." when I click the Add button in the Advanced dialogue box on the Exchange Server properties dialogue box.
Any ideas?
Thanks!
Barry

I'm getting the same thing. This problem seemed to start after we upgraded everyone to Office 2003. I found KB 833399 but can't find a system with an intact registry key. Nothing appears in LostAndFoundConfig. Users who already had a mailbox added don't seem to have a problem.

Help!