So I just hooked up a midi controller keyboard and started playing around with it to play sounds from Rapture.  Sounds great and lots of fun.  But sometimes (lots of times) when I change a patch and try to play it - no sound comes out (or a loud nasty pop) - it almost seems like it hits a virtual overload protection circuit in Sonar.  I can press play on the project after this and see levels in the console view from the other tracks - but no sound out to the speakers. I close sonar and then open the same project not changing anything and the synth sounds fine and so do all of the other tracks.  Weird huh?  Hitting the reset audio engine button has no effect.  It almost seems like the issue does not happen if I turn the output of Rapture down before playing the sounds from the controller.  After the restart of Sonar, the synth plays fine both from the controller and from the recorded midi.  The volume of my DAC-1 is turned down to reasonable or even low levels so this is not hitting the protection circuit on my monitors.
 
As a side note - this also happened before to me when trying to use a Slate Red compressor on a mono track - a loud unpleasant burst of noise then no sound from the project although the meters are showing signal.  Even removing this offending plugin didn't solve the issue - had to restart Sonar.
 
Is this a sonar issue (feature) or could this be something else?  I thought it may be due to this virtual instrument, but as you can see it happened with a normal VST plugin (that has a known issue with mono tracks in sonar).  Is there something within Sonar that acts like a virtual overload protection circuit? or are there certain situations that hork the audio engine and there's nothing left to do but restart sonar?

What version of Sonar are you running?

Sonar Platinum Ipswich 64-bit

There is no "protection circuit." It sounds like the synth is failing at some point. I have other reports involving DPro where a user was trying out a lot of programs and the synth went bad. Maybe this is the same issue (they both use a similar sfz engine). If Rapture fails on a particular program, it would be helpful to post the name of the program.
 
There have been issues reported with VST3 mono plug-ins which will be addressed in the next release http://forum.cakewalk.com/FindPost/3311327

Thanks for the reply.  This happens on many of the patches.  I'm at my day job now so I'll have to check it later to get the details.  I have the synth outputting to its own stereo track (using input monitoring) and then to a stereo buss.  BTW I updated to the latest version of Rapture through CCC. 

ok...just happened again.
changed patch to TB Ghost in Resonance
Hit the keyboard to play it.
Short burst of sound
Clipped the master buss fader by +0.6 after turning the output of Rapture down
Sonar hung this time.  Had to close it and lose my work.

I could not make Rapture to fail by switching to "Absolute 110 - TB Ghost in Resonance" in a 44.1K/24 project.
Are you using the 64bit Rapture VST version 1.2.2?
 

Could this be a matter of the patches lingering in system memory and thus maxing it out at some point as the patches accumulate (and causing the nasty sound/failure/silence)?
 
Pretty sure I've read about that happening.
 
I personally experienced the DPro issue that manifests itself this way but that was ages ago (and of course a totally different synth).

I went ahead and deleted the instance of Rapture and then added a new one and it seems to be working for the moment.  Maybe this instance got corrupted or something.  Yes I believe this is the latest version of Rapture 64-bit.

Rapture silent treatment happens to me after overloading the processor. This can happen right away or while performing.

Certain midi notes can also trigger it. I had a couple of midi filters in my track template to protect rapture from certain messages that came from my gr20. I find with rapture pro I don't need them.

To troubleshoot, you might start recording then go through your steps then use event inspector to figure out if a particular midi message caused the problem.

With mine, I could take the midi recording and play it back and cause the rapture silent treatment. This problem was usually caused by stepping on the patch change pedal in my gr20.