This happened to me today. Last night I left my phone charging on my PC through the USB port. PC was off, but USB is still powered. Phone was on.
The next morning, after I woke up I noticed that when I pressed the power button nothing happened. I plugged the cable off my PC, then back on, and the led was staying lit up red. Nothing when I pressed the power button again. No fastboot, nothing.
Finally, I plugged the phone using the original Sony adapter to the mains. It showed the Sony logo and it started charging. At least, so I thought. After a couple of hours, I checked the charging progress and nothing, battery was showing empty. So I tried to power the phone on while still charging. It booted Android and it was showing charging, but 0%. I powered the phone back off, it immediately started charging and battery progress was about 80%.
My guess is that somehow battery stats files were corrupted/deleted. Luckily the phone did not get bricked. I am on Android 4.0 ICS.