This isn't a new issue, but I think it is one that needs to keep getting brought up until it's fixed.
We need to be able to ban people from rejoining games. Until that happens, it at least needs to be possible to kick someone without the game completely locking up. More often than not, after the crash, it isn't possible to log back in to get another game going because of the "invalid username/password" message while the server resets.
This is _really_ annoying, especially when some a-holes abuse it to be funny.