Installed new NIC on NT4 - now dialup RAS doesn't work (?)

[NT Guy]

I've got a machine running NT4 server with 2 or 3 internal modems that
are used for after-hours dial up connections into our network. When a
connection is made, the client machine is given an IP address like
192.168.2.186 through .189. NetBeui is also bound to the adapter for
browsing and accessing network resources and for connecting to the
MS-Mail server running on another NT4 machine.

I recently swapped out the 10/100 NIC for a 100/1000 NIC card and
thought everything was fine. I had full network connectivity to that
machine, etc.

But when I make a dialup connection, sure I get connected, and I can
still connect to the MS-Mail service on the other NT4 machine, but I
can't ping anything beyond the machine I'm dialed into (I can ping the
machine - but I can't ping beyond it).

I've looked at all the bindings for RAS and they look ok.

It's been a few years since I've set these machines up, so I'm a
little rusty here. Where should I be looking to fix the bindings or
the TCP links between the modems / RAS service and the LAN ???