Here’s a little cautionary tale for anyone who uses VPN connections at all – after installing this week’s “scurity update” for WinXP, KB943460, you won’t be able to VPN out any more. Attempting to connect will give you the message “Error 800: Unable to establish connection”.
This situation is typically associated with restrictive local firewall settings, such as Norton Internet Security installs, but I don’t use that and since I was able to connect on Tuesday, I eventually was able to pinpoint the problem. Once I de-installed that “update” the VPN connections all work again.
MS has a support article on this update (see http://support.microsoft.com/?kbid=943460) where they explain a registry hack to allow certain applications, if you are having trouble with them, to bypass this security enhancement. But since I don’t know what the executable is for VPN connections (I doubt it works like that anyway) that doesn’t help much.
This is also listed as a “critical” security update so most likely you are going to have to manually uninstall and then tell WindowsUpdate to ignore this update in future, unless someone can tell us how to work around the issue…