Audio Export not working for me

Trying to export a project which has just 2 audio tracks, but can't get any sound either as .wav or MP3.  The files get created, but the audio is not being moved over.  It just ends its effort to export really quickly.  (Both tracks have been selected, and they play fine in the project.)
 
I'm using Sonar X3 Professional, 64 bit.  I'm selecting Entire Track to be exported in 16 bit.  Any ideas why this might be happening?  Thanks.

Also see what happens when you try to export Hardware Outputs. I assume you have mp3 licence ...

Do it like this (if not already)
 
Before export, select track 1 (to be sure you're not focused on the buses)
Do: Edit -> Select ALL  (All tracks should highlight)
Do: File -> export, audio... and select "Entire Mix" for the Source Category in the export dialog box.
Type in a file name and click Export.
 
If this don't work, well I just don't know. :-)

Are any soft synths involved?

Try "select none"   often select all does not work, but select none always works. 
 
I've always used what ever the default setting is,,, In 5 versions of Sonar I've never changed my export settings other than changing 32 bit to 16 bit for CD's. 
 
But I've often had tracks missing from the mix when I used Select All. I read on the forum here to use Select None and that has resulted in 100% success ever since for me.