So I went back and did several experiments.  With few exceptions the results are not too surprising.  Playback is done with ASIO buffer set to minimum (to reproduce output while tracking added vocalists.)
1) Frozen with Fast bounce, ASIO buffer set to minimum while bouncing -> lots of clicks and pops
2) Frozen with Fast bounce OFF, ASIO buffer set to minimum while bouncing -> occasional clicks and pops
3) Frozen with Fast bounce, ASIO buffer set to Maximum while bouncing -> 2 or 3 clicks and pops (in entire track)
4) Frozen with Fast bounce OFF, ASIO buffer set to Maximum while bouncing -> 2 clicks/pops
5) Frozen with Fast bounce OFF, ASIO buffer set to Maximum while bouncing, closed then re-opened Sonar -> NO clicks or pops (I assume indicating RAM needed to be freed up)
6) bouncing to clips, ASIO buffer set to Maximum while bouncing -> several clicks and pops (but reduced from pre-bounce)
7) I opened another similar project from same recording session, that has NO Melodyne editing, ASIO buffer set to MINIMUM for playback -> ZERO clicks / pops.
 
What I still don't understand is why a Frozen or a bounced clip will generate this noise consistent with CPU being over-utilized, when it doesn't happen with simple audio tracks.  There is NO other Fx or processing going on, this is a very simple project.  After bouncing the Region FX clips of Melodyne editing disappear, as I would expect, but there is still noise as if the processing is going on; similar (although not as notable) with a Frozen track.

In case anyone searches and finds this thread, I'm posting the solution.  It turns out the OP is a bit dense (that would be me).  Checking out some other threads on noise and comping, I realized I had not deleted my muted clips from the multiple vocalists after comping - and that those are all still being processed even though they're muted.  Additionally, I had not bounced all my vocalists' Melodyne edited clips; so even though muted, those were requiring bigger chunks of processing.
 
All I had to do was delete muted clips, and bounce the rest of the Melodyne-edited clips, and the problem is solved.  As is usually the case, a dash of user-error mixed with lack of thinking leads to problems.

MorganT - cool, you had me worried for a second there. Helpful to see the story unfold.

Can you put Solved in the thread name?