My 64GB has done that once since I bought it when they first came out. I had it on charge and the screen had come on while charging, while it was in its case. Once it cooled down the LCD was normal.
Whenever I charge it the screen comes on, so I just hit the red button once to turn it off and things are good.
I'm not sure why the screen comes on when connecting and disconnecting the PB, but it does and that can cause it to get hot.
