Windows update does not work

I installed Windows2000 pro as usual. Then I usually run “windows update” for all critical updates, security patches, and updrades to IE. However this time, when I run windows update, after checking it says “There are no updates available for your computer” which is impossible. Usually after a fresh install I have over 20 critical updates. I manually installed from IE5 to IE6 to see if this would help, but still the same problem. I checked with another workstation, and windows update works finethere. I am at a loss what to do, as I do not want to leave the system, with security patches not installed.
HELP