I had been playing ~30 minutes & was placing dirt for the last minute. When I broke a dirt block by hand, the game froze and crashed. Although this may be coincidental, the "destroy" animation never completed; the particles were still floating were the block was.

I don't know anything else about the issue--this didn't seem to be on a chunk border, nothing crazy was happening with redstone or mobs... the only "oddity" is that the game is 194 MB. Otherwise this is any old world.