Client dev log: http://bit.ly/1ajw9F7
I started up my MC survival world, spawned beside 5 furnaces... and could not click into the game windows then said "Java... is not responding" so I closed MC, but then my windows explorer crashed along with Skype and Internet explorer.
Update: Only happens when I play a world, save, leave the window for a while, come back and open a world. Did not crash my other java app's this time though.