Outlook connectivity to Exchange 2000

I am running Exchange 2000 in my main office. I have a satelite location that is connected using SonicWalls on either end with a vpn connecting the two. The satelite location pc’s are running Outlook 2003 and 2002 at various stages of updates. Two of the users can connect the the Exchange server and the rest cannot. there are a total of 7 users at that location and they can all connect to the network drives and i can get Outlook configured and the user name is resolved, but when trying to connect to the email folders i get a mesage that says “unable to display folders”. Any feedback would be greatly appreciated.
Thanks.