I used Lumia 800 and I met the simliar symptom as you mentioned. But you can solve the issue by your self.
1, charge the phone for more than 10 minuts.
2, Disconnect the charger.
3, Press power on key to swith on the phone.(The phone must be disconnection with charger)
I have the same issue. Phone won't turn on whatever I do. It did this once or twice before and I was able to get it back on pretty quick, not this time though. Completely dead.