A friend and I want to play co-op, just the two of us.

I set up the game as private co-op, put in a password and start the game... and I'm in a team of a bunch of players. I invite him, and he can't get in. WHat's going on?

anyone know?

I had a similar problem trying to play with my brother. My problem however was no matter what game mode i picked, the co-op option in mode setting was always grayed out. I had to start a campaign and once in mission had to invite xbox party. That would start me off with all bots and then my brother would replace one once in game. So this works way works if your trying to play together. Again this was only tested in the campaign mode so I couldnt tell ya about Public or Private games.