Screen not working after connection to PC

Hi, I connected my TZ70 to my PC and downloaded pictures to the hard drive and then disconnected the cmaera from the PC without powering down the camera. SInce then, the display screen on the Camera does not work normally - it displays the “turn off cmera to charge” messagee when connecting the camera to the PC but stays reolutely black when in either “take picture” or “show picture” mode. Any ideas?