Unable to edit. Black screen - poor performance - high power usage

Since the last update, I am unable to edit videos.  After importing a small H.264 .MOV file and dragging it over, nothing appears in the Program window or Source window if I try to play it there - just a black screen.  Also, PP is now using a lot of system resources - it didn't before.  Also, when manipulating the program, I get a lot of "(Not Responding)".  This software is useless to me now.