My lowest panel is changing from the editor window to the rendered view ORIGINAL:

Have made several videos successfully but suddenly my [render] button does nothing but change my lowest panel from the editor to the result view


http://i.imgur.com/dWC89iW.png

changes to


http://i.imgur.com/UJhUGJp.png

I also noticed it does pop up "Sequence Render" for a very fast moment in place of the blender version above preview. I've never had this happen before and when I try to find previous mentions for help I get bogged down in threads about 3d rendering. I've not changed my settings except to increase the Sequence/Clip Editor Cache. I've checked my properties to make sure those are the same as before. Dimensions, fps, start and end frames, output folder is correct, encoding is the h264 preset, ac3 audio.
It turns out the problem was that I had a combination of two issues.

Firstly, I have about 3 minutes of blank video so rather than showing black the preview window shows the gray background that is throughout Blender. This made me assume it wasn't working because it was not black, but really it was just transparent.

Secondly, I set it again, then left to make dinner. Turns out it takes a long time to start up (I guess). I've watching it right now and it is creating the video at about 2/3 speed of original footage in the preview. This is largest video in blender by about double in time and also my first 1080 rather than 720. I guess I was just too impatient.  

The important thing is I learned some stuff today. :)