
The solution in the end was to run SpringLobby as administrator in Vista. I already had spring.exe setup to run as administrator, and I thought that would be enough. Clearly not!
Below is my original post:
I've read a few threads on here about LAN games, and they didn't help my problem, so I' m making this thread in the hope someone can help

The setup
I have two computers on a LAN (connected via a router):
Computer A: Desktop running Vista.
Computer B: Laptop running XP.
Both are connected to the router by cable, not wirelessly.
I've been trying to get a LAN game going by using SpringLobby. Both computers can access SpringLobby's multiplayer section through the internet. I've tried several setups but cannot get the two computers into a game together.
Setup A
Computer A hosts the game on SpringLobby. I leave "test firewall" unticked and choose "none" under NAT traversal. Computer B joins this game in SpringLobby no problem. I start the game. Computer A (the host) gets loads the game and I can move the commander around etc. Computer B loads the game, gets to a screen where it says "Connecting to server" breifly, then switches to "Waiting for server response". On this screen it also says:
Server: Computer A local IP
Local endpoint: port 0 UDP
Computer B does not make it past this screen.
Setup B
Computer B hosts the game on SpringLobby. I leave "test firewall" unticked and choose "none" under NAT traversal. Computer A joins this game in SpringLobby no problem. Both computers load the game. Computer B (ths host) shows both computers as players and counts down to game start. Computer A shows only Computer A as a player, and the game begins (I can move the commander etc). The game begins on Computer B, and immediately says that I've won.
Setup C
I use Computer A to host the game, using the "relay battle to autohost" option. Computer B joins this game in SpringLobby no problem. oth computers load the game. Computer B shows both computers as players (as well as the relaySteve autohost) and counts down to game start. Computer A shows only Computer A as a player, and the game begins (I can move the commander etc). The game begins on Computer B, and immediately says that I've won.