VPN and TCP connection establishment problem

This has troubled me for some time now, and I would be endlessly
grateful if someone could help I figure this out.

I have a Windows Server 2003 EE (enterprise edition), running the
Remote Access & Routing Service, and I connect to this computer using
the default VPN configuration. I choose to use the default gateway on
the remote network, and I can browse the web through that computer, as
expected.

However, I have another application I use, which does not work as
expected. Now, recently I have upgraded some hardware in my machine,
and reinstalled the OS, and now this all stopped working.

Could hardware changes start causing unexpected server behavior!?

Because everything worked fine before the hardware changes, and believe
me when I say, that the hardware is not damaged or malfunctioning in
anyway. I really do think that this is software related. Since is
appeared after a reinstall of windows.

This is were I get confused.

Using Ethereal i've managed to find out that when the application tries
to establish a TCP connection, the VPN server replies an incoming
connection attempt (on the configured port) with a RST packet. The idea
is to route all traffic through the VPN server, but for some odd reason
the connection is not forwarded properly.

Now the application already has a Telnet chat setup on that port, could
this cause a conflict, or is there some policy that i've missed with
causes the server to prevent several connections on the same port?

And another thing, for some reason all search queries sent as UDP
packets from other users of the application is received by my local
machine running the application, and users can download from my
machine, running the application, but I can't seem to establish a
connection successfully. Also, upon searching the search result is sent
as UDP datagram's to the server, received there, but not forwarded to
my
machine.

All these things have worked perfectly before, but this new
installation is WIN2003 SP1, again, is there some setting that I have
not overlooked? The MTU is set to 1300, so that should not be an issue.

I'm very grateful for anyone who takes the time to understand my
problem, and help me.
Regards
John