Uh.. My party was searching for a matchmaking game... We couldn't find a game... So I backed us out.
One of us went to another game.
Another started a campaign level.
The other two of us just sat at the menu.
After about a minute, it puts us two into a lobby with other players, and asks us to vote for a map.
When he backed out, the guy who went to campaign was prompted to vote for the multiplayer map, but was able to cancel it.
Us two that entered the matchmade game lobby could see that it appeared the campaign guy was still in our game.
His name was one of the players on the list.
So the map voting process ended, the game went to start up, and the guy who was in a campaign level, had his GAME FREEZE.
It tried adding him to the matchmaking game, after he left the party and was playing a campaign level.
The two of us who got into the game are now stuck on an endless loading screen.
I wish the the best of luck to the engineers tasked to fix this game.