The subject behavior is probably the result of NOT having the Messenger service started.
NOTE: The Messenger service is disabled by default in Windows Server 2003.
To resolve this issue:
1. Right-click My Computer and press Manage.
2. Expand Services and Applications.
3. Press Services.
4. Double-click the Messenger service.
5. Select the General tab.
6. Select Automatic, in the Startup type drop-down list, and press Apply.
7. Press the Start button.
8. After the Messenger service starts, press OK.
9. Close the Computer Management dialog.