I'm using Arturia's V Collection 5 and Spark2 plugins with SONAR and I've run into a very concerning issue.  Occasionally when I'm switching between preset sounds I get an EXTREMELY loud popping noise and I have no idea what's causing it.  I've mostly noticed it happening when I have multiple synths and Spark2 running together.  Once it happens, if I do anything - like click on the plugin window to change presets - it keeps happening until I've restarted SONAR.  

This is not the usual buffer pop sound, it happens when playback is stopped.  These are dangerously loud, like yanking cables out of a live input at full volume, and I'm afraid it's going to blow a speaker.  The mains level doesn't affect it at all, even when mains are turned all the way down the pops are still crazy loud.  I bought my first pair of studio monitors a few months ago and I can't afford to damage them.

Is the plugin crashing?  Could my buffer settings cause this?  I'm using the VST2 versions of the V Collection plugins, and Spark2 is VST2 only.  Does anyone here have a clue what is going on?  How can I protect my speakers from this?  

I've posted over in the Arturia forums about this but never got a response.  

Are they loud pops that stop or are they more like feedback loops that won't stop?

It's not a loop, it happens when I switch from one preset to another by clicking on the plugin window.

Can't you use a limiter?

RSMCGUITAR
Can't you use a limiter?

The sound seems to be independent of the tracks/busses.  Limiter doesn't make a difference. That's why I'm confused about what's causing it.  Main volume doesn't affect it either.

Are all the separate plugin instances routed to "Midi Omni" or the same midi channel (example: midi channel 1)?  If they are, try assigning each plugin to its own midi channel (1-16) and see if you still have the problem.
 
Also, the noise will be coming from all or one of the plugins.  Watch your VU meters for each track and see if they all spike or just one or some do. 

I'm using separate MIDI and audio tracks for each, with each synth using a different MIDI channel.  (4 channels, two keyboards with splits.)  I'll keep an eye on the meters, but I don't remember seeing anything peak when it happens.

Can you see your CPU performance? It seemed to be the deal with me. I had to fix the CPU Core balance. :)
 

could be a video issue if it's only happening with the gui open

11Dreams
Can you see your CPU performance? It seemed to be the deal with me. I had to fix the CPU Core balance. :)

I hadn't thought of that.  Which settings did you adjust?  I've got a 6-core CPU, I'm pretty sure I have the horsepower for this kind of thing.

Use Multiprocessing Engine - check
Plug-in Load Blancing - no check
Use MMCSS - check

MMCSS Thread Priority - 2
MMCSS Task Key - Pro Audio