Question : 0x80072F78 Error using Windows Update

I've spent the whole day on this - and finally narrowed it down to a bizarre behaviour that I don't understand - need help!

I've got a mix of 35 W2K and WinXP PCs on a network - all connected to a common gateway (We're on a domain, but internet traffic doesn't route through the servers).

Whenever I attempt to download and install any updates (on any PC) the browser takes me to the windows update site and tries to check for an update to the windows update software - after about 4 minutes it times out with error 0x80072F78.

Checking the WindowsUpdate.log file I see that the system is trying to download a file called wuredir.cab from (1st) download.windowsupdate.com and then (2) download.microsoft.com - on both occasions this fails.

Here's where it gets interesting - if I attempt to browse to http://download.microsoft.com on any of these PCs it tries for 30 seconds or so, and then comes back with a message saying that it can't connect - however, if I try to connect to any other site (eg www.microsoft.com) it connects just fine.

It gets better ...

One of the computers has a modem and a dial up account with another ISP - if I connect to the internet via that it connects to the download sites just fine (redirecting me to their downloads website) - and if I check the Windows Update with DUN running it works just fine - kill the dialup and it won't update again.

I've tried connecting to the site via another ISP and from another site - and that works OK too.

So - it looks like either a Router (Cisco 800 series) or ISP (Telstra Clear) problem - I get on the phone to the ISP - they login to a router of theirs using our username and password - and they can browse to the site no problem - which tends to point the finger back at our Cisco ADSL router (perhaps).

Food for thought ...

Updates have always worked just fine through this router - and it hasn't had any configuration changes in the last couple of years - plus - it happily connects up to any other site in the world, so why would this one be any different?

Additionally, I've ...

Searched the Microsoft KB (no, we're not behind a firewall; no, we're not using a proxy server) - and done the usual (restarted everything a few times - started and stopped services - emptied temp files etc etc etc).

ANY IDEAS ANYONE? - Issue is 100% repeatable - occuring on IE6 and 7 - on WinXP and 2K - on workstation, and server - I'm starting to get a little thin on ideas.

PS: We can PING download.microsoft.com - just not connect to it.

Answer : 0x80072F78 Error using Windows Update

Sorry, I really haven't been much help.

Not to a lot the ISP would likely do to cause problems, but it's possible changes on their end could require lowering the MTU, which is why I was suggesting it.

Swapping the router should at least confirm if it's the ISP or the router.