Immediate out of sync error, but only when playing mods

[Beginner]

Me and a friend are trying to play a direct IP multiplayer game(since I get "Could not create network socket" error if I click LAN), but if we try playing with mods(tried with Fall From Heaven, Rise of Mankind, and Final Frontier) we get out of sync error immediately after starting the game. I've checked, we both have the same version of the game and mods. The strange thing is, if we simply play without mods there's no problems at all. Unfortunately, playing without mods gets boring really fast, so any solution to this problem would be greatly appreciated!

I run Windows Vista, he runs Windows 7, in case that has something to do with it.

 

[Lemon Merchant]

Some mods are not MP compatible. Check the forums for the mods you mentioned to find out.