It happened to my Surface 2 today. After I rebooted, it was in the process of installing updates. Not sure if that had anything to do with why the lock screen froze. For me, Surface 2 has been a lot more buggy than my original Surface RT. I'm actually on my 2nd Surface 2. The first one I returned because of the crashing, pixelated screen issue mentioned in another thread. And another thing happened to me today. I was charging my Surface 2 and when I tried to turn it on to see if it was fully charged yet, it wouldn't turn on. I tried a few times, but nothing. And it was extremely hot. I unplugged the charger and was able to reboot it, so now it appears to be working again. Never had an issue like this when charging my Surface RT. The charge had reached 100%, so to me it seems that it didn't shut off the charging once it got to 100%. It just kept trying to charge, which would probably explain why the Surface and the charger were so hot. Weird. I've got mixed feelings about Surface 2. The screen is better and it seems a lot zippier than my Surface RT, but it seems less reliable.