LCD display blank

I have a Toshiba PDR-M4 DC. I can view previously taken photos, and the specifics of the camera (ie the time, date and battery, etc.) are all visiable on the screen. However the LCD screen itself is blank (black) and when I've tried to take a picture through the viewfinder, the picture when viewed is also black. I refered to handbook and it says that the camera is in PC mode and to return it to photography mode. If all that means is to turn the knob on the top of the camera from d/l mode back to picture taking mode -- they must think we're complete idiots!! Any suggestions?!?!

Thanks for looking.
Heather