Setting up Windows 2008 R2 Std as Internet Gateway

You were able to create a dial-up VPN connection between Vista and Windows Web Server 2008 without the Network Policy Server role? If so, I'm curious as to what the subnet/IP looked like to the client in that scenario once the tunnel was up.

If you have a VPN up, then you've transferred your problem domain from one of VPN to one of routing. I'm pretty confident that you'll be able to bridge connections using the Web edition and that you can also use Internet Connection Sharing. If not, there are cheap and possibly free "internet sharing" programs available (NAT32).

This assumes that your client machine somehow has an IP on the server's (internal?) network.

Also, when you say Internet traffic, it's possible your definition may include only traffic that is proxy-able. In which case you can shift the domain again from routing to proxying, and use a free proxy server bound to the IP on the other end of the tunnel.

Those Dead Gateway Detection DWORDs are useless on Windows Server 2008. The only reason they exist is for compatibility reasons. The TCP/IP driver and Windows router components don't look for these values anymore.

I suspect this feature was rolled into Auto-Tuning, which debuted in Windows Vista. Try executing the following in an elevated command prompt (and reboot):

netsh int tcp set global autotuninglevel=disabled

Update (added September 13, 2009 @7:58PM EST)

If that doesn't work, we'll need more diagnostic output. Start a (circular) trace with either the NetConnection or LAN scenarios and let it continue running until the problem occurs.

netsh trace start scenario=NetConnection maxSize=512

_{(Example: Starts the NetConnection tracing scenario, with a maximum trace log size of 512MB)}

You can open the resulting trace in Network Monitor 3.3, just make sure you install the latest parsers.