Still a problem in 13w36b.
Yes, still a problem in 1.6.2.
Not resolved in 1.6.2 prerelease.
I ran an experiment today. I left it idling in game all day. When I got home, I returned to the menu, loaded a different game, played for a few minutes and then switched workspaces. When I came back it had hung again. So wherever the problem is, its not cleared out by quitting and restarting the game.
I don't know if any of this is helpful. I'll keep playing!
More info. It only seems to happen in-game. If I sit at the menu it doesn't hang.
I have the same problem. Oracle Java 7 (1.7.0_25-b15), Debian unstable, kernel 3.9.8. It does it with both Intel and NVidia drivers, so it doesn't appear to be a driver problem.
It doesn't happen every time I switch away. It might be time-dependent - the longer its off screen, the more likely it is to occur.
Still a problem in 1.7.2.