MP problems

[techathon]

Hi. Me and my friend are trying to have a MP game online, but it keeps on giving us error messages that say "You failed to connect to host. Connection timed out" or something like that. We checked the exceptions for firewall and even tried turning off our firewalls alltogether. That didn't work so I turned back on my firewall and checked here. It lets other random people join games that we started on both our cpus.

PLEASE HELP

I am running XP and my fried is running Vista, is that a reason?