First, this problem has existed for almost two years. Until serverfault was born, I pretty much gave up on solving it - but now, hope is reborn!

I've set up a Windows 2003 server as a domain controller and VPN server at a remote office. I am able to connect to and work over the VPN from every windows client I've tried, including XP, Vista, and Windows 7 without issue, from at least five different networks (corporate and home, domain and non.) It works fine from all of them.

However, whenever I connect from clients on my home network, the connection drops (silently) after 3 minutes or less. After a short while, it will eventually tell me the connection has dropped and attempt to redial/reconnect (if I've configured the client that way.) If I reconnect, the connection will re-establish and appear to work correctly, but again will silently drop, this time after a seemingly shorter time period.

These are not intermittent drops. It happens every single time, in exactly the same way. The only variable is how long the connection survives.

It doesn't matter what type of traffic I send. I can sit idle, send continuous pings, RDP, transfer files, all of that at once - it makes no difference. The result is always the same. Connected for a few minutes, then silent death.

Since I doubt anyone has experienced this exact situation, what steps can I take to troubleshoot my evanescing VPN?