Normally I can play XBL games fine with no problems on my school network. I tried playing the RE5 demo coop with my friend and we could just not connect at all. I tried it with someone else and we couldn't connect either. I use a router, so I DMZ'd to the 360's IP address to escape having to worry about any port forwarding. I don't think there is any major firewall to speak of. I thought it might be the network but I've played fine in the past. Is there something else I should be on the lookout for?