Green scrolling bar won't stop, just keeps going

Hi,

Running SBS2K (Win 2000) and I cannot get the critical updates to run.
I get through to choosing if I want to install by express or custom, after
which it comes up with the checking for updates screen with the green scroll
bar.

This screen does not progress, the green scroll bar just keeps going, i've
left it for 20mins & still not made any progress.

I'm certain the system has no viruses or spyware on it.
I've tried restarting the system.
I've tried uninstalling the IE Objects related to the update site.
I can confirm there is no firewall in the way.

Please help, as I'm all out of ideas.

Thanks,
Gav