I haven't heard of that one before. You could try reinstalling and also updating your video drivers. If that fails, take a screenshot and post it on the official D3 Beta forums, but also include your system specifications and operating system and hopefully they can help you
Did you actually take a pic with your camera? Because the best way to do it is hit "print screen" on your keyboard, and then just open paint or any image editing program, and use ctrl+v to paste and it will have taken a computer generated screenshot of whatever was up at the time
Not sure if it would help but try this,
While you are on the login window, Press Alt+ Space, then press M, then Move your mouse or use the arrow keys to move it.
Hope that helps.
I had an issue like this with Boarderlands when it first came out. Tried everything and Gearbox asked me to post a screenshot of the problem. Every time i Prnt Scr it just took a picture of my background or the game as if it was fullscreen. ;p These things annoy me easily so i rage uninstalled the game. Derailing this guy's problem.