can't connect to 10.0.0.x from windows server 2003 (after update)

Hello Folks!

I have a weird problem for which i simply cannot find the solution for the
last couple of hours *grml*

I've installed a Windows 2003 Server on a Virutal Machine (Virtual PC 2004).
It worked pretty well, everything looked good. As my Internet modem has a
preset IP adress of 10.0.0.138 i decided to assign 10.0.0.188 to my Server.
No problem so far.... i hat internet connection instantly and went for the
latest security updates (which is recommended after installing Windows Server
2003).

After rebooting the PC (Virtual Machine) the network connection didn't work
anymore.... a couple of hours later i know this much: it has to do something
with the ip-adress-range.... because if i set up the ip to 192.168.0.1 and
some other pc in my network to 192.168.0.2 networking works fine.

if i try exactly the same with 10.0.0.1 and 10.0.0.2 i simply dont get a
connection. But my whole network is based on 10.0.0.x addresses and on top of
that my internet modem can't be set up so easily to 192.168.0.x address
range...

Do you have any ideas or suggestions? - As i said... before security update
(which i did over the internet!) it worked fine... afterwards: dead wire

Sincerely
Wolfgang