canvas disappears when I click on it.

Hi,

I am adjusting to CS6 on a Windows 7 machine, and cannot figure out why clicking any part of my canvas with either the bounding box tool, select path tool, or text tool make the canvas disappear. 

The file, and all of its layers were working fine--allowing me to edit as I had in CS 3 (the last version I used).  Suddenly, I'm unable to edit text because if I click on the line of it, the work area goes dark!  Clicking on the MOVE tool recovers the usual view. 

Have I inadvertantly changed some mysterious setting? If so, I'm incredibly frustrated about a problem that should be easy to detect and fix.

Thanks,

Caroline