bwbalint
Craig/JonD

Do you have a link to the USB PCIe card that is exclusively for audio?

Thanks!

It took me a moment to realize you meant "exclusive" as in the PCIe-supplied USB ports are devoted exclusively to the audio device.  In that sense, yes, that's correct.  A definite improvement over the typical USB controllers shared between other USB devices -- and then there's the added benefit of the PCIe bus having greater bandwidth. 
 
As Craig implied, you can buy these cards anywhere, and just about any will do the job, assuming your audio interface isn't too picky about the USB chipset.  You should go to your interface's support site and check out their knowledge base.  In some cases the devs have done their own testing, and have helpfully provided a list of chipsets that will (or won't) work with their interfaces.
 
It also wouldn't hurt to Google "USB chipset" and "your audio interface" and see what others have experienced. 

AdamGrossmanLG
Cool beans, will try this first tonight, when I get home.  Thank you for the input.
 
It is weird that my MIDI controller works with stand alone VSTS and not Sonar, so one would figure it is Sonar... but I will try this setting first and report back here.

Thank you for the help!

So did you get it working?

Okay - I'm chiming in as having the same (or similar) problem as AdamGrossmanLG. I've also had the problem, on and off, for years - thought I'd fixed it a couple of times but it comes back :-(. It used to occur more often when starting Sonar but it has progressed to frequently occurring during record and playback. 
 
The problem is when I stop playback or record of a track in a project containing a MIDI track(s), my system freezes (but I can still play a soft synth with the MIDI controller! - just no response to keyboard or mouse). It used to happen occasionally but now with 2017.07 it occurs VERY frequently. Sonar (still) also nearly always hangs at the splash screen. My workaround for both these issues has been to unplug and replug my USB MIDI controller - that frees up everything and I can proceed once the MIDI device is recognized again by Sonar.
 
After reading this thread, I did find that USB suspend was enabled but disabling it had no effect. I also followed Craig's procedure for disabling audio devices. I had no duplicates but VIA High Definition Audio was active (which I did not expect) - I removed that as I recall it had been a problem in the past. I imagine it got reinstalled with my new Dell Monitor software but not sure.
 
If anyone has more ideas how to diagnose or correct this issue, I'm all ears! It can no longer be ignored since it has become such a huge pita for me. I may temporarily revert to an earlier release but I prefer to move forward instead of backward.

You could also check individual USB devices in "Device Manager" to make sure "Allow the computer to turn off this device to save power" is NOT enabled :-)

Yes, I did that while I was in the device manager. Thanks for the suggestion.

I assume you have a sufficiently high MIDI playback buffer value? I have it set to 1500 ms. I think the default value is too low, and often leads to MIDI issues that are solved by increasing the buffer value.
 

TStorms
I also followed Craig's procedure for disabling audio devices. I had no duplicates but VIA High Definition Audio was active (which I did not expect) - I removed that as I recall it had been a problem in the past. I imagine it got reinstalled with my new Dell Monitor software but not sure.

 
It's not just about audio devices, but about the MIDI Port Limit. Try following the advice in this article.

Im sorry I havent reported back here yet.  I have been too busy.  I will try this tonight though for sure and report back here :)

I mean I will try everything in this thread one at a time.  I will report back with a detailed report :)
 

Anderton
I assume you have a sufficiently high MIDI playback buffer value? I have it set to 1500 ms. I think the default value is too low, and often leads to MIDI issues that are solved by increasing the buffer value.
 

TStorms
I also followed Craig's procedure for disabling audio devices. I had no duplicates but VIA High Definition Audio was active (which I did not expect) - I removed that as I recall it had been a problem in the past. I imagine it got reinstalled with my new Dell Monitor software but not sure.

 
It's not just about audio devices, but about the MIDI Port Limit. Try following the advice in this article.

Thanks Craig. Yes - MIDI Record buffers are 128 and Playback is 2000ms.
 
That article is the "Craig's procedure" I was referring to. In addition to the advice in the article I also checked the driver level and other properties of all audio and USB devices to ensure they were up to snuff. Additionally, I disabled HD Audio in Device Manager and also in my BIOS.

Well in that case, I'm stumped. Any problems I've encountered in the past were solved by what I mentioned.