Tv's set to hdmi, but when I plug-in the hdmi cable, the computer screen goes totally black, and because of this, I can't do anything! When I unplug the hdmi cable from either the tv or laptop, I get my computer screen back ........ it's driving me NUTS! I read in one of the MANY 'forums' that I've been on to try and get to the bottom of this, that when ALL screens are 'black', you're supposed to hit either Fn/F4 or Fn/F5 to get something to 'mirror' ...... is this correct?