You cannot download updates when you access the Windows Update Web site from
a Windows XP-based computer that is behind a firewall or a proxy server
[Error number: 0x80244017], [Error number: 0x80244018], [Error number:
0x80244019], [Error number: 0x8024401B], [Error number: 0x80244021]
John Dough posted:
IE it showed I wasn't using one.
Running "proxycfg -d" fixed it all up."
Another user reported that clearing all cookies and temporary internet files
solved his problem and he was then able to install the update.