As far a PCM failsafe and how things can happen. Here's a very real scenario that has happened, and may have happend in this case.

If the radio went into failsafe for whatever reason, and the pilot is reacting like Kevin said, and is bending the sticks on his transmitter to control the plane with no results.

What do you think is going to happen when that reciever comes out of failsafe. Bingo - SNAPROLL. You've got the sticks bent all over the place, the plane going to react once the signal is clear, and plow right into the ground.

From experience, when you think your in failsafe, don't over control the sticks, if you can't control yourself from doing that, let go of the sticks entirely, and wait a couple of seconds, and see if you got control back.