That was the only thing I could come up with as well, but I am using the EC3 connectors that have one square side and one round side. They cannot be plugged in backwards without a lot of force. I learned a long time ago, as I am a get a bigger hammer kind of guy, that most things in this hobby dont react well to being forced so I am sure the pack was plugged in correctly. I have used this pack before so I know the polarity in the connectors is right. The only thing I can come up with is that the ESC just failed which then fried the motor.

Can a brushless motor be rebuilt??? Just wondering, it maight be nice to have a spare or use it for something else.