Problems playin on LAN

[ZerXes]

Hey!
Me and a friend are trying to play OpenTTD together on LAN but has a problem.
when I host a game my friend finds it but when he tries to join the game freezes för like 10sec and then he can choose to start a new company but as soon as he presses the button he is disconnected.

If he hosts I cant find his game at all, I cant even find any games online so the problem is probebly on my comp.
We both run Vista64 SP1, I have no firewall that can block OpenTTD...

any suggestions?

[JapyDooge]

Is'nt it also that the internal Windows firewall is still active?
What antivirus do you use?
How is the LAN 'designed'? Just a few computers on a router using DHCP (automatic IP addresses)?