Aaah - I see, so your VPN connection between your outside XP pc and router is up and running, but you cannot access your ubuntu machine on the LAN side of the router. I actually cannot help you there as I have the same problems myself. On http://wlhdd.co.uk/wiki/OpenVPN it says to add the following to your server.conf:
Code:
 push "route 192.168.0.0 255.255.255.0"
However it does not work on my machine. I have also tried:
Code:
 push "route 192.168.1.0 255.255.255.0"
It seems more logic to me, but this does not work either. I can access the samba server on my router, but not any of the other machines on the LAN. I guess I have to look at the openVPN documentation to find out how to do this - stay tuned for an update to this.....

BR,
René