Screenshot of the development console upon opening the launcher, before clicking Play...on my Mac the console is filled with dozens of lines indicating resources are being downloaded, but in Windows 7 this is the only response I get. I also tried on two Linux machines and was successful both times; in my testing the problem seems limited to Windows, but this may not be the case for others.
I've encountered the same issue. Launcher displays a triplicate notice that "YOU CAN CLOSE THIS LAUNCHER IF THE GAME STARTED OK", and then three messages from the client indicate that I've been logged in. Last message is "Client> 2013-07-11 11:17:25 [CLIENT] [INFO] LWJGL Version: 2.9.0" and then no more activity, and no client window open.
Just lost 2 horses wearing diamond armor on my server (version 1.6.2). They were the last two horses to be ridden and the only ones to vanish. Strangely enough one of them was tied to a post and the rope was still visible but the horse was gone. We use a nether gate system to travel if that makes any difference. Luckily I had a recent backup.