Okay, the grinding sound might very well be the gears either running against their housing or there mesh is way to tight. I would check that. If the mesh is super tight i will loose engine power and might explain why your battery only lasts 2 minutes.
The heli should not just tip over on its own. Assuming you are not giving any stick imputs it sound like you have a glitch. I suggest you desconect the pinion of the motor to the gear it turns. This will allow you to do a range check without the thing taking off. With the antenna completely closed take roughly 50-60 steps away from the heli. If you see it start to flutter its controls try rerouting the antena. If it continues to faill you have to start elimating would could be wrong. Continue your range checking with one servo unplugged from the channel. If it continues plug that servo back in and remove the other one. Continue this untill you are sure all servos are functional. Other things to test are gyro, reciever (reciever crystal), and in the worst case, your transmitter. Other things you can do to avoid glitches are making sure all electronics and wiring are spaced as far apart as possible, and you can buy a glitch reducer from helihobby.com.

Good Luck