Here is the scenario:
You are set up so that everyone gets dropped into a Lobby before they can join one of your meetings.
You have an IM conversation going with a Federated contact. You decide it’s time to add a whiteboard. So you add in a whiteboard but the remote federated contact basically gets dropped. In reality, they get bounced into the Lobby.
That isn’t supposed to happen. They should be able to see the Whiteboard and skip the Lobby.
Here is the Microsoft Technet article on the issue.
Except the fix in the article doesn’t work. This has not yet been patched on the client. The only real fix is to have the user disable the Lobby.