When I import a midi performance from RB into Sonar X3, my custom midi tracks cut out.  Anyone else have this issue? Anyone know how to fix this?  Thank you. 

Try increasing the MIDI Prepare Using Buffer to 500ms it isn't there already.
 
Preferences > MIDI > Playback and Recording

Thanks brundlefly.  Unfortunately, your suggestion did not work, though I believe the answer is in the preference settings.  Why would RB midi file be different from the Sonar X3 files???? Aaaararrrrrghhhh!
 
EVENT LIST has a blue KEY AFTERTOUCH event at the very top.  In my preferences, KEY AFTERTOUCH and CHANNEL AFTERTOUCH are not marked.  Could this be the problem?  Be right back.   Nope, that wasn't the problem.  (sigh)
 
EUREKA!!!  Save the file as a wav. THEN import into Sonar X3.
 

Could a controller 7 = 0 volume message be getting in there somewhere?

I assume you are talking about my Sonar X3 midi tracks?  
How do I check that?