SBS 2003 VPN suddenly fails with 691 after reboot

Question

After allowing two seemingly inoccuous Windows Updates (KB2388210 and KB982632) our production Windows Small Business Server 2003 (SP2) required a reboot.

After the reboot all VPN connections failed with 691.

Things I have confirmed so far:

The Password is being verified as there is a different error with a wrong password.

The server EventLog entry says "The user [domain]/[username] has connected and failed to authenticate on port [VPNport]. The line has been disconnected.".

The router and other external infrastructure is not relevant as we can confirm the same issue trying to VPN from a machine on the local network.

We believe our "Accounting Provider" was always None, but changing it to Windows didn't seem to change any thing.

We do have ISA sticking its nose in, and attempting to reset VPN settings from there changed nothing.

_{(This has been "cross-posted" to the Microsoft SBS Forum)}

Answer 1

For other reasons we intended uninstalling ISA Server at the end of the week anyway. Seeing as it may have been the cause of the problem I uninstalled it now.

That brings up the CEICW again, but doesn't let you use existing Broadband/Dialup settings. Nevertheless most of what it offered were useful defaults. It did let me not change the rest of the options.

CEICW ran successfully after ISA was uninstalled.

VPN then failed with 800.

I noticed the next step in the Server Management To Do list was Remote Access; ran that and it set up VPN again, and all is well again.