VPN/Firewall

I have a VPN tunnel connected with a remote Win 98 user
who needs access to our network.

Currently we can get her connected using Remote Desktop
Connection. Actually neither side can ping the other's
internal computers, just the VPN router.

There isn't a firewall on the remote user's computer and
the computer that she needs to log into is ready for
access for an external source.

The boss has an exact setup (remote computer to log onto
work network) and it has been working perfectly for a
couple of months. (I can ping the boss' home computer)

I'm quite the novice in this area, but could there be
some firewall somewhere blocking the remote user's
connection? Or could it be something else? I would
appreciate any leads on this, as I'm starting to get some
pressure from the boss to get this working.

Thank You
Ted