Bah... after playing around for a long time all I know is that I can't route my way out of a paper bag!

Seems I can't reach any of the Windows PCs on the network inside the VPN (though curiously a Windows CE device is reachable...). I played with routes, MTUs, etc. all to no avail. I can reach (a) myself on the other end, (b) the DNS server, and that's it... I guess I will be dropping an e-mail to the networking crew at work to see if they're interested in helping me find out what's going on.

[Edit]

Well, it turns out things may have been working... there was a power outage so most of the PCs were off. I guess the networking guys already know about my troubles as MPPE encryption is now required for VPN access... I've tried compiling the apt-get'able kernel source and quickly hit script/compiler errors, so it looks like the end of the line for me. Hope the above info was helpful to someone.

[/Edit]