you will need to find out what ports file transfer msn messenger works on and forward those ports to that computer.
what is happening if the request is going to the router, and the router doesnt know which computer to forward the port too. (i believe file transfer is port 6891-6900)
from another site:
"Both incoming and outgoing TCP connections use this range of ports: 6891 to 6900. This allows up to 10 simultaneous file transfers per sender. If you open only Port 6891, users will be able to do only one file transfer at a time."
but alot of times i see people having problems with file transfer behind NAT routers with no sucess
what router do you have and do you have the latest firmware installed on to the router?
maybe something can help you here
http://www.microsoft.com/technet/tre...oy/worki01.asp