Lost Planet troubles....

Ok, so i just got a 360 last week and ive got lost planet for it. Ive got it all hooked up fine and everything but ive got one problem. Whenever i play lost planet on live The only match types i can play are "Connection A" and "Connection B" None of the "Default" matches will work. Does anyone know what i need to do to fix this. The majority of matches are on the default setting so it makes it a real pain in the rear. Im guessing Its something to do with my router settings or something. I dont really know though.

Thanks for any tips anyone can give.