I ran into this too. In my case, it turned out to be the 7TV extension. After disabling or updating it, the chat input came back immediately. In the meantime, CamSurf is a great alternative for random video chats.
I often want to quickly check a webpage and then return to the same conversation without losing context or waiting for the chat to reload. Keeping the session alive until the user explicitly closes it would be a big usability.
