Why is Windows Update suddenly failing with error 0x80244019?

Since installing updates yesterday, one of our 2008 R2 servers refuses to connect to our WSUS again and, instead, reports the unknown error 0x80244019. Connecting to the official Windows Update repository works without any issues. The problem happens only with our local WSUS.

The Windows support website on the error suggests:

If you receive one of these errors while downloading updates, the most common cause is a computer virus that has turned off Windows Update, or another service on your computer that is needed by Windows Update.

I'm gonna vote No on that one.

My WindowsUpdate.log shows the following:

2012-09-13  13:00:52:738     892    5c0 PT  +++++++++++  PT: Synchronizing server updates  +++++++++++
2012-09-13  13:00:52:738     892    5c0 PT    + ServiceId = {3DA21691-E39D-4DA6-8A4B-B43877BCB1B7}, Server URL = http://SRV-PDC/ClientWebService/client.asmx
2012-09-13  13:00:52:769     892    5c0 PT  WARNING: Cached cookie has expired or new PID is available
2012-09-13  13:00:52:769     892    5c0 PT  Initializing simple targeting cookie, clientId = a6c96caf-d9ca-4f31-a003-827e7089ff64, target group = Server, DNS name = srv-exchange.porta.haseke.de
2012-09-13  13:00:52:769     892    5c0 PT    Server URL = http://SRV-PDC/SimpleAuthWebService/SimpleAuth.asmx
2012-09-13  13:00:52:957     892    5c0 PT  WARNING: GetAuthorizationCookie failure, error = 0x80244019, soap client error = 10, soap error code = 0, HTTP status code = 404
2012-09-13  13:00:52:957     892    5c0 PT  WARNING: Failed to initialize Simple Targeting Cookie: 0x80244019
2012-09-13  13:00:52:957     892    5c0 PT  WARNING: PopulateAuthCookies failed: 0x80244019
2012-09-13  13:00:52:957     892    5c0 PT  WARNING: RefreshCookie failed: 0x80244019
2012-09-13  13:00:52:957     892    5c0 PT  WARNING: RefreshPTState failed: 0x80244019
2012-09-13  13:00:52:957     892    5c0 PT  WARNING: Sync of Updates: 0x80244019
2012-09-13  13:00:52:957     892    5c0 PT  WARNING: SyncServerUpdatesInternal failed: 0x80244019
2012-09-13  13:00:52:957     892    5c0 Agent     * WARNING: Failed to synchronize, error = 0x80244019
2012-09-13  13:00:52:957     892    5c0 Agent     * WARNING: Exit code = 0x80244019

And, actually, another support article caught my eye: 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

That article refers to XP, but I had to recently tweak with the WinHTTP settings on that server to resolve yet another issue (Please see the support article Error message when you import a third-party certificate into Exchange Server 2010: "The certificate status could not be determined because the revocation check failed" for further details).

I fixed that access problem by running:

netsh winhttp set proxy proxy-server="http=www-proxy:8080" bypass-list="*.domain.example.com"

So, I'm assuming Windows Update uses WinHTTP as well, and my changes prevent it from working properly. But even after adjusting my bypass-list to "*.domain.example.com;<local>", Windows Update refuses to function.

Seems like a reboot was all that was needed after adjusting the bypass-list, which must contain <local> so the WinHTTP proxy is bypassed for your local WSUS installation:

netsh winhttp set proxy proxy-server="http=www-proxy:8080" bypass-list="*.domain.example.com;<local>"

Alternatively, if you're already setting the correct proxy in IE (through group policy, for example), you can simply import those settings into WinHTTP:

netsh winhttp import proxy source=ie

To inspect your own current WinHTTP proxy settings, run netsh winhttp show proxy.