Midi issue with Sonar X2 Studio build 306

Hi. Have you tried to use TTS instead of Microsoft GS? TTS is SONAR's default default "MIDI player", I believe.
Others may know better.
All the best.

For the midi tracks in question - there is a default parameter/behavior with Sonar, that will automatically turn a button/feature called 'Input Echo' On when you bring that midi track into focus, and when you bring a different track into focus Sonar will be default turn the Input Echo Off once that track is no longer in focus (and the new track that is now in focus will have ITS Input Echo button turned on (Blue color).
 
Input Echo being On is what needs to be set for hearing sounds from whatever the midi track is sending its midi data to (like TTS-1, Kontakt, Dimension Pro, etc.)
 
You can also say, click on a midi track to bring it in focus and get its Input Echo turned ON, then manually click on the Input Echo buttons for other midi tracks, if you want to be able to hear those sounds as well as the sounds for the original track that automatically had its Input Echo on.
 
The Input Echo button will be to the right of the text window for the midi track's name, and will be gray if not on, or blue when turned on.  You can hover your mouse above the buttons there to get a little pop-up explanation of what the name of that button or knob is.
 
Perhaps the above might help?
 
Bob Bone