I'm having the same symptoms as dr1ft, after installing Nitdroid N12. I've flashed the phone many times, now it will not work. Tried just about every combination of holding U and putting in battery, connecting USB to no avail. The USB symbol actually does appear on the top right too but is useless. Battery was at 70% right before it started doing this.

With the battery in, even if the USB is inserted in just the phone and not a computer/wall charger it keeps showing the Nokia logo with no backlight and rebooting/vibrating.

Seems it's... gone...