That happened to me the other day, i installed some updates then i restart the phone and it boot normal but when i get to the screen i just was able to swipe up or down through the screen , can't open apps or do anything also it was on airplane mode. I try restarting again and after the AT&T logo instead of Nokia i got blue screen, I try to reset it and it didn't work. The only way to fix it was flashing the firmware again, so far the phone is working fine. My guess was that The Words With Friends apps had something to do. Here is the fix...I just installed 7Pass,the mobile of Keepass and after using it for a short time,the phone locked and the screen was blue Just like a real PC...how exciting!