have you checked to see if the receptacle is hooked up properly. If the neutral and one of the hots is reversed, you could be running 240 volts to parts that are 120 volt rated.
check the voltage, on the recep, from each hot leg to neutral and from each hot leg to ground and both hot legs to each other.
check the voltage, on the recep, from each hot leg to neutral and from each hot leg to ground and both hot legs to each other.