global address list not available

When I click on the address book in Outlook 2000 an error says “The server containing global address list is no longer available, you can reconnect to another server by restarting outlook or retry operation when the server is reachable”.

The weird thing is that after waiting a few minutes or after restarting Outlook, the global address list is availabe again. The rest of my colleagues encounter this too. I have already installed Office 2000 SP3.

Can someone tell me what causes this problem.

The server is using Windows Server 2003 and Exchange 2003

thanks and regards,