Outlook stops responding when connecting to another user's calenda

[Inky]

One Outlook account has delegates assigned to the calendar and can be opened
by these delegates on several computers but not on others. The problem is
that it "hangs" and never connects and Outlook will become unresponsive.
There seems to be no common denominator, it always fails on the same machines
but these are a variety of Win2K-XP with Outlook 2K-2003. On other machcines
of the same type and logging in as the same users it works just fine if
Outlook is trying to connect to the other user's calendar.

Any suggestions.