Why do my electric IMP gets hot?

without connecting my Electric IMP but only to the USB power supply, it gets really hot.
I have tested with another IMP in order to see if the April module has a fail or something, but it doesn´t.

The IMP gets really hot but it still runs the code.

What should I do?

Sounds like it has, at some point, seen a high voltage (either on power input pins or on an IO pin). What’s the mac address of the card?