That is weird. Have you tried the mods in question on various hosts, or is it only one of you who is trying to be the host? If there's one designated host, I'm thinking that maybe his computer doesn't have enough RAM... or something. I've never heard of a problem like that, so I'm just whistling Dixie.
You're probably not making this mistake, but just for the sake of completeness, are you sure that the host has the proper mods enabled?
Yeah, all of us have the same mod activated (we tried in turn New Cold War, Navy SEALS 2.0 and Royal Marines 2.1). Next time I'll try hosting, but I don't think its a hardware problem. We're all on broadband connections. Our host has a new 17" FP iMac with 512 of RAM, and I have a 1Gig Powerbook with 768 of RAM. I don't know the exact configurations of the other two guys but we've never had a problem with un-modded Ghost Recon. Just with the mods that we tried for the first time tonight. I just know its something trivially stupid that we are somehow overlooking...frustrating is all, knowing that we can play the mods in single player, and regular GR in MP, but not mods in MP. Grrr..
Anyways, thanks for the tips. I'll keep you posted.