I have a Yamaha keyboard that is both a  Midi controller using USB and my default piano instrument for my projects. Normally with a new project it works fine when I set the input to Omni and the  output to the piano. But with old projects that were created before I owned this particular piano, I always have trouble getting Sonar to play it properly. Because the project is old, the piano tracks are set to different ins and outs. I will set the input and output to the correct new settings, but it still won't play unless I "jiggle" it by hitting one of the hardware instrument selection buttons on the piano itself while playing back. Mind you, it doesn't do to hit the button before I start playback. So I have to hit Space to play and THEN poke one of the instrument buttons to get the piano to sound. I tried creating a new track in this old project and set the ins and outs there, but it's the same problem. How do I get it so that Sonar recognizes the new piano without my having to go through that?

No really, can someone reply?

Which Yamaha Keyboard?
 
Same problem with newly created sequences?
 
Have you tried cutting and pasting the old tracks into a brand new project?

It's a Yamaha P-105. Newly created projects are just fine - it only happens in projects created before I bought this keyboard.
 
I tried cutting and pasting into a new project, whose track was already set up for the proper output, though input was incorrect. Strange, when I first played back, no audio. Hitting one of the keyboard buttons this time, however, did not work. Then I changed the INPUT to Omni, and now it plays back fine.

Do your old projects have bank/program changes that are recognized by your new keyboard? Your description of "it doesn't do to hit the button before I start playback" sounds like the project sends a bank/pgm change at the start of playback.

The fact that cutting and pasting changes your symptoms with the old files indicates you may have some hidden data in the tracks.  I agree with bvideo that is could be some random patch/program change commands.  Check the event list for the tracks.  I always disable recording and sending of patch/program changes in Preferences since I can never seem to get them working right.
 
Also, that Yamaha P-105 may not have the most robust MIDI implementation.  Buy it seems you've been using it with SONAR for a while so you probably know better than me.