MIDI madness 2.0 - notes not playing

I posted a similar message to the Native Instruments forum, but I'm cross posting here because the Sonar community is helpful and knowledgeable (the NI folks, not as good).
 
I am likely making a novice mistake, but editing MIDI for Battery 3 is driving me nuts at the moment.
 
I loaded the jazz brushes kit into Battery, then dropped a MIDI loop into a track. The loop (which has the right timing) was hitting note D3. When I run the loop, the D3 note plays. So far, so good.
 
But I want C1, not D3. And I know C1 works because when I hit that on the keyboard, I get the correct drum strike.
 
But C1 in a MIDI track does not play on Battery. If I edit the D3 note to be C1, the meters in the MIDI track jump, but not the meters in the Battery track or synth. If I add a C1 to the same loop, D3 still plays but C1 is silent.
 
Any help is appreciated. 

Thanks 35mm. Sadly, that did not fox the problem. I changed the playback buffer spec (the only one I found umder MIDI preferences). Not using any plugins.

Thanks Billy86.
The keyboard is not the problem. I can hit C1 there and the correct drum plays. This indicates that Battery is listening to the omni channel correctly.
The defect then is in the Sonar midi track and the delivery of the C1 note.
Last night, on a hunch, I created a new midi track and drew a C1 note into it (bypassing loops and such). Same problem ... the note clearly plays in the midi track (meters jump) but not in the Battery synth (no meter action).