“Error 0x80072F8C: No description available.” When Trying to Use SUS on Windows 2003

I've just installed my evaluation of .net server RC2 Beta3, and I'm having problems after installing the latest copy of SUS server. When I click on "synchronise now" , I get an error:

Failed to download from URL 'http://www.msus.windowsupdate.com/msus/v1/aucatalog1.cab'. (Error 0x80072F8C: No description available.)

I have checked my proxy settings (I don't have one) and have also checked that I can see the file mentioned above through IE.

From the microsoft.public.softwareupdatesvcs newsgroup
In order to use SUS on Windows Server 2003 you should be using the RC1 build (3718) at a minimum. Check that you have this version, if not download a more recent version.