I've checked the xbox live forums, and I haven't found any real helpful guidance at all. Everyone just utilized the cookie cutter response and say, "Check your NAT/bandwidth/modem/router", then dust their hands off and walk away. The same is done here. This is an extremely frustrating problem, as I have successfully saved a couple of these instances, and have been cheated out of some accomplishments.
I understand there may be no real definite explanation, but I tire of everyone 'explaining away' these questions and issues, by giving generic responses and kicking the can out down the road.
This is a 343 game, so logically, 343 should be responsible for providing answers and proper resolves for these issues.