Why cant I host parties?

[Major2]

My download is 20mbs and my upload is 5mbs. So its not because of lag and it has nothing to do with my router or modem. But no matter who Im playing with, it can be any of the 20 plus buddies and it wont allow them to join my party and it wont let them pass room host to me. I can play game in every other way i just would like tp host every once in awhile. Any ideas fellas?

[Ramski13]

had the same problem last night with a few guys I run with - wouldn't let one guy host but would let me - we figured it had to be something to do with the map pack - does everyone have the new maps, that might be it.