One more thing: when I turn on the quadcopter (when everything was working), the 4 ESCs were activated and did some beeps. There was one of them that beeped differently from the others. When 3 finished beeping this one beeped one more time. Don't know if was the burned ESC. Can a uncalibrated ESC burn?
Detail: I discarted this possibility because my first 4 ESCs had the same calibration (don't know wich calibration but they came from the same place at same time and did the same beep) and one of them burned. After this I changed the ESC and then I heard a different beep, but everything worked at the first fligth, and only burned after the second fligth, while I was trying to re-activate the motors.
Other thing: when the props accidentally touched the ground them stopped, that's why I had to re-activate the motors, but this time they didn't re-activate.
Some times I even had problems with a single motor that didn't want to activate, like this:
http://www.youtube.com/watch?v=CEEhNKRgkdU but after some tries it worked