I have just purchased a second hand copy of Miroslav Philharmonic. The set up went well and I have no issues with it until I try to change a soundbank. As soon as I do that, I get an audio dropout message which can last from 5 to 30 seconds. When the audio engine resumes, the soundbank has changed and all works well. I have no other vst's running and no audio tracks, only Philharmonik. You can see my computer configuration below so I wouldn't think that's an issue. The CPU meter in Sonar is sitting very low so it doesn't seem to be an issue with CPU usage either. Has anyone else had similar audio dropouts and, if so, how did you fix it?  

That sounds right considering you are loading a new bunch of samples. 

The only input I have here is that if this is the original Miroslav, it was a 32 bit engine based on the SampleTank base, I believe.  Probably the SampleTank 2 engine.
 
IK Multimedia have now released SampleTank 3 and a new version of it called Cusom Shop, the idea being that it is the engine without the samples and you can purchase new sample to load into it.  It also happens to allow the import of all old format SampleTank sounds.  I don't know if this will work for the Miroslav library or not, but I would think it could.
 
I have the original SampleTank 2XL and SonicSynth 2 libraries and I was able to import all of those into this new engine.  It doesn't sound any different to me, but the interface is new, not as small, and the scroll wheel works (!). 
 
You have to import the samples and the instruments.  It can take a while to do and you have to have double the disk space, as it makes copies of all of the files.
 
The only caution I have is that the VST3 version doesn't seem to work as well as the VST2 version in Sonar for some reason.
 
Here's a link to the Custom Shop: http://www.ikmultimedia.com/products/sampletankcs/
 
Hope that helps.

Philharmonik is a 32bit program which I run under BitBridge. I will try the SampleTank suggestion and see how that goes. Thanks for that idea. With a bit of luck, it will help stop the audio dropout problem.

I have both versions of Miroslav and I always have one articulation per midi channel. I also have projects with multiple instrument instances in MP, where each instrument loads multiple channels. I have no issue switching articulation in a project with many MP instruments/articulations. The VST3 version is not useable, imo. The VST2 version is stable and what I've used.
 
I'm not sure what you mean by "changing soundbanks", other than loading a new instrument or articulation: You need to define those ahead of time, load before playback, and then switch in realtime.
 
This is what works well for me. Hope this helps.

Thank you for all your help. I tried the SampleTank route with VST3 and it was not happy. With VST2, on the other hand, the audio dropouts have now been eliminated. Great suggestions from all. Thank you.