I think i fixed the problem i had. I went into my linksys router settings, clicked the 'advanced' tab; clicked into the 'Port Forwarding' tab, and enabled 3 of my ext.ports that were disabled that my xbl uses. I tried playing online after i had done so and i played for about 2 hours without any disconnections.

I can't contribute to any help because i share your problems. I can play any game from Halo to call of duty to red faction, play maybe one match or less, and then get randomly disconnected. However i can go to the guide and reconnect within seconds. I have a motorola modem connected to a Wireless B router that i use to connect to my xbox via ethernet cable. My NAT is disabled and Ive just found no way to fix this problem. Help?