For you guys having issues it may be worth considering doing a hard restart of your console. I know nothing of how this problem happens for Halo, but in the past I have had decent to spotty connections and had trouble playing games online. If you have the system set to always on mode instead of power saving mode, your router can sometimes get wonked out by the consoles staying idle while in its hibernation state. When you do a hard reset, by holding down the power button for 10 seconds or changing the always on to power saver mode, it can sometimes fix a bad connection that may be causing matchmaking issues. If use power saver mode already, ignore this.