"Attempt to join queue failed"

Friend and I queue together for normal blind pick. A match is found, we both click accept.

I enter the champion select screen. My friend is also listed in champion select, but he does not enter champion select, he remains on the home screen. I get a pop-up error message stating "Attempt to join queue failed, because a player is already in a game.". Friend says he got an error stating only "attempt to join queue failed."

He was listed in champion select, but his status icon in the friends list was green, indicating he was out of game. We could not figure out a way to get him in game.

Then, of course, leaver buster says we have to wait 6 minutes......