track view doesn't move thru measures when playing back

When I am playing back a project in track view I only see the timeline until it reaches the end of my screen. for example I start at measure 1 and can see measures 1 thru 35.  After it passes 35 I no longer see any movement.  But this is while it is playing back.  I don't know what I did.  The same project works fine on a different computer.   also if I stop and hit rewind from the end of the song my view stays at the end even though playback starts at the beginning.  What is this? 

Yeah, sounds like you've pressed the Scroll key on your keyboard.