While playing 13w39b, I entered the End and then rode a minecart a short distance. After the cart reached a certain point, the audio kept playing, but the cart stopped moving on the screen. I was able to turn my character within the cart, but could not exit the cart or cause it to move. I could even break blocks within range of the cart, but these blocks did not drop any item entities.

When I paused the game and attempted to exit to the main menu, I got stuck on a "brown screen" (the screen with the dirt-block texture which displays when a level is loading). I never ended up being able to return to the menu, and was always forced to force-quit the application.

After restarting the application and reloading the world, I was back on the 5x5 obsidian platform (the entrance to the End) as if nothing had happened. I was now able to walk along the minecart track where the game had frozen earlier. When I reached a certain point, the blocks simply stopped (despite the fact that I had built a farm at.that location previously). At this point, when I logged out I was again subject to a brown-screen game freeze. At the moment, my world is unplayable as a result of this glitch.

As a side-note, after the glitch had occurred a few timed I tried to load up the world in an external editor (mcedit) in order to move my character back to the Overworld, so that I could continue playing. However, loading up the world caused MCEdit to crash as well.