Can't Join on Halo Severs

When having an open NAT and a solid connection and being hard wired into my modem, I can now no longer connect to the Halo matchmaking servers. If I use wireless off of a router in my house I can get a connection, but it results in lag. I have no issues with Gears of War, or any other matchmaking. I have called my ISP, and Xbox multiple times. I didn’t have this issue at launch or during November, why now? I get a red triangle at the matchmaking screen saying I can’t connect. I have Comcast internet.