Hello,
Are you using ISA as your proxy server? If so, please check out the article
below
This KB basically has a list of URL’s that you configure ISA to allow
anonymous access to the Windows Update Site
http://support.microsoft.com/kb/885819
Diana Smith [MSFT] <>
CSS Security Team
This posting is provided "AS IS" with no warranties, and confers no rights.
"George" <> wrote in message
news

C7C39BC-69B7-402C-B9BB-...
> Used proxycfg tool with -u switch to set WinHTTP proxy settings to the
> browser's manual proxy setting.
>
> After clicking Custom link on Windows Update page an error page is
> received.
> The listing of updates failed.
>
> I am using an authenticating proxy and presumed authentication failed.
>
> Used WinHTPtraceCfg tool to verify my assumption.
>
> <<<<-------- HTTP stream follows below
> ----------------------------------------------->>>>
> 22:50:18.613 ::*000000a* :: HTTP/1.1 407 Proxy Authentication Required
> 22:50:18.613 ::*000000a* :: Proxy-Authenticate: BASIC realm="Client Public
> Internet Access Proxy"
> 22:50:18.613 ::*000000a* :: Cache-Control: no-cache
> 22:50:18.613 ::*000000a* :: Pragma: no-cache
> 22:50:18.613 ::*000000a* :: Content-Type: text/html; charset=utf-8
> 22:50:18.613 ::*000000a* :: Proxy-Connection: close
> 22:50:18.613 ::*000000a* :: Set-Cookie: BCSI-CSC0552F45=2; Path=/
> 22:50:18.613 ::*000000a* :: Connection: close
> 22:50:18.613 ::*000000a* :: Content-Length: 858
> 22:50:18.613 ::*000000a* ::
> 22:50:18.613 ::*000000a* ::
> 22:50:18.613 ::*000000a* :: <<<<-------- End
> ----------------------------------------------->>>>
> 22:50:18.613 ::*000000a* :: "www.update.microsoft.com" NOT resolved
> 22:50:18.613 ::*000000a* :: WinHttpSendRequest: error 12007
> [ERROR_WINHTTP_NAME_NOT_RESOLVED]
> 22:50:18.633 ::*000000a* :: Using proxy server: my_proxy.com:80
> 22:50:18.683 ::*000000a* :: sending data:
> 22:50:18.693 ::*000000a* :: 231 (0xe7) bytes
>
> Is there a configuration paramter for entering authentication credentials?
>
> --
> George
> Internet Administrator