Hm, I have a weird problem... Islands like eastborder won't load in MP. I just get an error that say "Cannot load eastborder.wrp" or something like that and the game exits to desktop. I don't have this problem in singleplayer... If I have the island preloaded into memory before MP and the same island is used in the chosen mission there's no trouble.
I hope it doesn't bother you too much if I go and preload an island if a mission that we play is on e.g eastborder. I'm not sure with what islands I have this problem with, but I think it's only some FDF islands.