Exchange Server Unavailable

Hi,

I have a Small Business Server 4.5 running
Exchange, which is used for distributing
public folders. The clients use Outlook 2000.

Recently, when the users start Outlook, the
program hangs for some time and reports the
error

"Exchange Server unavailable."

The users are given the choice of "Retry",
which may or may not work, or "Work Offline",
which means that the public folders are unavailable.

The Exchange services seem to run correctly,
and all other network services (logon,
mapped drives, e-mail) works fine. The
network runs on TCP/IP only, and all
computers have fixed, private IP adresses
(192.168.1.x/24). It all worked fine for
about a year, until today!

What can I do about this?

Best regards,

Rolf Nordeide.