I was on 4.0.4. I saw a software update notification, and I clicked it. The update was about 35mb. It downloaded successfully. But when I selected to install it, it first took more than 30 minutes. Now, there is nothing, just a black screen. Not sure even if the phone is ON or OFF.
P.S. While doing all this, my battery was very low. So, I had the phone connected with my laptop to give it power. Now I can see only the black screen (as if phone is switched off) and the orange light near the speaker is blinking that usually blinks to indicate charging.