Error opening Outlook for the first time

[Sean]

Hi,
When I turn on a PC that has Windows NT and open Outlook 2000 for the first
time I get the following message:
'Your Microsoft Exchange Server is unavailable'. It gives you the following
options: 'Retry', 'Work Offline' and 'Cancel'. When I click 'Retry', it
connects properly after about a minute. I only get the message the first time
I open Outlook after I turn on the machine. The server is Small Business
Server 2000. It has only started happening in the last week.
Any ideas?
Sean