You could try increasing a couple of buffers within Sonar, that they for some reason changed their initial default sizes to some time ago.  Sometimes, folks resolve sound issues by doing the following:
 
1) Launch Sonar - do not open a project, just close the Start Screen when it opens with Sonar.
2) Hit the letter 'P' on your computer keyboard to enter Sonar's Preferences dialog box
3) Click on 'Sync and Caching (this is under the Audio tab)
4) Increase the File System's: Playback I/O Buffer Size (KB) to 512 
5) Also increase the File System's Record I/O Buffer Size (KB) to 512
6) Click Apply and close Preferences
7) I don't know that you have to - but you might consider restarting Sonar, to get those larger buffers.
8) Try out something and see if it works better
 
I run with these 2 buffers set to 512, and some folks even use larger ones than that.  I also record at: 24-bit bit depth, 48 K for Sample rate, with an ASIO Buffer Size set to 128.  My Total Round Trip Latency, as reported by Sonar, is around 10 milliseconds.
 
I am running on about 15 minutes of sleep, so I HAVE to go lie down, but I will circle back to this thread once I get some sleep, and hopefully some other folks will help get you sorted out.
 
Also, make sure for these tests - don't load up a bunch of effects into the open project, as one or more added effects could require higher latency to work properly (not all effects plugins are meant to be used while recording - because they can add loads of latency to do their thing.  Things like 'Look Ahead Processing' indicate that the plugin needs to read data ahead of where it is currently at in the Now Time Marker, and that adds loads of latency, which is FINE when you have jacked up the ASIO Buffer Size to 1024 or 2048 for mixing).
 
Bob Bone
 

Thanks Bob.  I tried changing the Record and Playback I/O buffers as you suggested, but it didn't seem to make a difference even at the max of 2048.  I also tried experimenting with different combinations of sample rates and buffer sizes, but nothing below 192 gives me clear sound with no pops (regardless of whether I'm at 44.1kHz or 48kHz).  At that setting my total roundtrip latency is 14.8 msec at 44.1kHz, and 13.6 msec at 48kHz. 
 
My normal buffer setting of 64 does the total roundtrip in under 6 msec, and everything works fine.  RPro just doesn't want to cooperate.         

Have you run resplendant's latency monitor on your PC? It's a free tool.

Latency Monitor says my system "appears to be suitable for handling real-time audio and other tasks without dropouts."

I know that the original Dimension Pro and Rapture both responded to hot keys that would adjust their sample rates internally.
 
I wonder if this is also try for Rapture Pro - where there may be a way there to also adjust sample rate used by Rapture Pro.
 
It has been so long since I looked at the hot keys to control this that I forgot which keys are for which sample rates.  I think they were something like micro host keys or something like that.
 
If nobody else jumps in with that info, I will be back online in a couple hours and will look to see if I can find the info.
 
Bob Bone
 

The stand alone mode is documented in the RPro user guide. The keyboard shortcuts for the stand alone mode start on page 138.

These are the ones I saved off for Dimension Pro and the original Rapture.  I think they are the same for Rapture Pro.  I cannot recall.  I remember I set the Sample Rate for all 3 programs running them one at a time in stand-alone mode and then hitting the key to set the sample rate per my desires - which for ME was F4 to set Sample Rate to 48000.  I do not recall if these programs play their samples back in Sonar using the sample rate set in stand-alone mode or not:
 
ESC: All Notes Off
F1/F2: Open/Close z3ta+ Editor (mainly for testing purposes)
F3: Set to 44100
F4: Set to 48000
Shift+F3: Set to 88200
Shift+F4: Set to 96000
F5: Transpose -12
F6: Transpose -1
F7: Transpose +1
F8: Transpose +12
F11/F12: Previous/Next Program
Left/Right arrows: Bend down/up
Up arrow: CC1
Down arrow: CC2
Space bar: Aftertouch
 
(MIDI) Notes:
ZSXDCVGBHNJM,L.;/Q2W3E4RT6Y7UI9O0P-[
 
Anyways - Hope the above helps.
 
Bob Bone
 

The stand alone settings do not affect the plug-ins when hosted in a DAW.

Have you tried Asio?

gswitz
Have you tried Asio?

Yes.



Thanks for the input guys, it's very appreciated but I'm not sure where to go from here.  The DPro and Rapture legacy libraries work fine with no audio pops or crackling.  It's only the RPro library that is causing the audio problems, and I've found that it also has several broken patches with missing multisamples.  I'm not sure if the patch problem is related to the audio issue, but it might be worth mentioning.

It doesn't make sense that I would have audio problems with one library and not the others.