Requesting Data From Exchagne Server

[Anton06]

I have several users with in our company that are receiving "Requesting Data From Exchange Server" when the click into the Calendar. Outlook opens to the Inbox, then they try to navigate to the Calendar, and bang they sit there while the server sends back thier information. I check the IM, and it is disabled. The server resourcers look fine. Quad 700's with 2Gb of ram for 800 users.

Client Config
Win2k, with Office XP, and outlook XP/2002

Server Config
NT 4 SP6a, with Exch 5.5 SP4 apart of a Windows 2003 domain.

All suggestions are welcome!!!!!