This seems to be a problem only when you are doing Internet connection sharing from what I am able to glean. I am running a server with 4 NICs, Adapter Teaming, public and private IP address and I have absolutely NO problems. I can connect to the server via LAN or Internet. I have verified the proper IP address connection via a "packet analyzer".
The problem may be resolved by changing your servers port to something like 992. I believe the problem is that Windows gets confused because the pass-thru client and the server are trying to use the same port number, but that is just conjecture.
Try this and let us know if it works: flserver.exe /p992
Your clients will then need to add this: freelancer.exe /s<yourserver's IP>:992 (unless it shows up on the Global list then they will know what port to use from there).
Hope this helps... my apologies if not.
Arcane
www.oldmenonline.net
Frontier-Station SysOp