I have AutoCad LT 2014 for Mac.

This morning all of a sudden, when I open up a new drawing or open up an old drawing, my drawing window is just blank and when I move my cursor or arrow across it, it dissapears too.  When I click, like to start drawing a line, the numerical displays show up, so its like the drawing is there but hidden behind something.  I just have a blank charcoal screen with all my tool bars showing but can't see my drawing.  Any suggestions....?