Well I just noticed this now at home, because I've been having a problem with playing on XBL.
My NAT settings are apparently set to Moderate, and it's screwing up my games.
It's a new router. Linksys WRT160N. I have UPnP enabled, DMZ disabled, and Port Forwarding disabled. NAT is turned on. Newest firmware. Tried rebooting modem/router/360 to no avail.
How do I change it to open? Please I'm begging you guys, I need this solved...quick. :'(