Tripecac
I just noticed something very strange, and it could just be a coincidence.
 
After I stopped working on my project, I ran my usual backup script, which uses rysync to backup my project files locally and remotely.  I've been using the same script for more than 10 years, but for some reason, for the first time ever, rsync failed, giving me a STATUS_ACCESS_VIOLATION error.  I tried again, as administrator, and got the same error.  It didn't matter if I was rsyncing locally or remotely.
 
I then restarted windows, and tried again.  This time it worked.
 
Could the rsync issue possibly be related to the Sonar/Focusrite issue???  Again, this is the first time I've ever seen rsync fail like that, and the only thing I've done since rebooting earlier (after the BSOD) was use Sonar.

Probably not, but since you are getting a BSOD, that does tend to implicate a bad driver, or worse, a failing hardware component. Sonar will definitely expose a bad driver, but it will not cause an audio interface to fail on its own.
 
Dan

Not a fan of Focusrite's WDM driver, I tried it as well and while I didn't get a BSOD it was choppy and gave me dropouts.
 
Word of advice to help troubleshoot Focusrite issues try downloading their free version of Ableton Live. I can almost guarantee if you call or email their tech support they will tell you to do that. If the problems occur in Ableton it will help them help you troubleshoot the issues. I spent a lot of time with them on my problems which happened in all my DAWs.
 
Just an FYI, after 45 days I gave up my Scarlett this past winter and swapped it for a Behringer UMC 1820. The drivers aren't quite as good, but it's been a much more stable experience for me. I can go as low as 1.5ms which gives me a round trip of 4.9ms. Plus there has been zero ghost in the machine issues.

Some experienced tech type folks are leery of factory techs saying right off the bat to load the free versions of different software packages just to see if "it works" or "what changes". (Like loading Ableton and Reaper or similar).
That answer from them is an automatic reply the factory techs use. Like have you rebooted...etc.

Odds are an interface dll, template, bit rate, or hidden sys file will change and it could work.

But it won't help narrow your setup specific problem.*Many, many others are using the Focusrite successfully on a variety of DAWs.
It likely would have been better to take the Interface to a different computer.

It's not a step other software houses do when they also maintain the hardware and computers themselves.....later they know they have to deinstall, as well as deal with any new conflicts on the computer those actions may cause.

I don't think 35mm had on a "Sonar is best" hat on when he responded..

That said it's always exasperating when dealing with this type of problem. Good luck, hope it works out quickly.

I'd just like to reiterate something:
 
I work at home, and listen to the Scarlett all day long (probably about 15 hours/day).  I listen to nusic, videos, and all sorts of games...  I never have any problems with the Scarlett normally.  This is why I don't suspect a hardware fault, or a USB port conflict.
 
It's only when I fire up Sonar that I have problems.  Sonar is the only application I have which uses the Scarlett's ASIO driver. And it's only when I am using Sonar/ASIO that I have this problem where after a few minutes, the audio cuts out and won't come back until I restart Sonar.
 
All other applications use the "normal" driver, which is labeled "Focusrite USB" in the Sound list.  I'm not sure what type of driver it is, but it obeys my multimedia keyboard's volume controls, which the ASIO driver does not.
 
Like I posted yesterday, when I tried get Sonar to use the WDM driver instead of ASIO, I got a BSOD.  So, Sonar is stuck with ASIO.
 
My instinct at this point is to see if Drumlab (a NI synth which came with Komplete 11) is causing the problems.  The last time I had a Scarlett-related problem it was an aggressive arpeggiator in a NI synth; it didn't cause exactly the same error, but did cause lots of short dropouts and crackle.  When I disabled the arp, the dropouts stopped.  I noticed that the arp causes the number of voices in that synth to skyrocket.  My conclusion at that time is that if a NI synth has "too many" voices, then either Sonar or the Scarlett gets confused and can't handle it.  Since my Drumlab track is peaking at about 60-70 voices, I'm suspecting that it is pushing the boundaries of what Sonar or the Scarlett can handle.
 
So here's my question:
 
What is the easiest way to prevent Sonar from using a particular synth, without removing the synth from the track? 
 
I don't want to lose whatever settings I changed in that Drumlab instance.  I tried simply muting the track, but notice that it's still "doing stuff", reaching 60-70 voices, so it seems to be still doing its processing; only the audio output it muted, not its processing.  Is there a better way to prevent the Drumlab instance from doing anything?
 
Also, I never freeze tracks, but this is one case where I'm contemplating it.  I'm concerned that freezing will have some disadvantages, based on my brief experimenting with it a few years ago:
 
1) Rendered audio consumes a non-trivial amount of disk space.
 
2) I have to remember to un-freeze the track and delete its rendered audio after mixdown (or right before mixdown).
 
3) If a track is frozen, I will feel discouraged from making edits to it (since I'd have to unfreeze, edit, refreeze each time).
 
4) If I want to copy sections of a frozen track to other parts of the song, I have to worry about fade in/out in order to avoid pops and clicks.
 
Do those disadvantages still persist in the current version of Sonar?  Or has working with frozen tracks become easier in later versions?

I think these are super questions for our Cakewalk friends

Well, pending an answer to your question from someone more knowledgeable:  Here's a "quick and dirty" way to tell if your NI synth is the culprit:
 
Open the project (turn OFF Auto save if it's enabled), delete the synth and mess around with your project for a while (without saving it obviously)...... record stuff into it, add tracks, try some other synths etc etc.  If your audio engine crashes, then it's NOT the NI synth that's the problem.  If the project hums along OK, then it might be the NI synth, or a combination of things involving the synth. 
 
Still suspect a conflict somewhere in your Window computer rather than Scarlett.

Tripecac
 
 
What is the easiest way to prevent Sonar from using a particular synth, without removing the synth from the track? 
 
 
I don't want to lose whatever settings I changed in that Drumlab instance.  I tried simply muting the track, but notice that it's still "doing stuff", reaching 60-70 voices, so it seems to be still doing its processing; only the audio output it muted, not its processing.  Is there a better way to prevent the Drumlab instance from doing anything?
 

Just use the disconnect button in the Synth Rack view
 

Also, I never freeze tracks, but this is one case where I'm contemplating it.  I'm concerned that freezing will have some disadvantages, based on my brief experimenting with it a few years ago:
 
1) Rendered audio consumes a non-trivial amount of disk space.

Should be totally irrelevant in these days of multiple Terabyte drives
 

 
2) I have to remember to un-freeze the track and delete its rendered audio after mixdown (or right before mixdown).

Why? Bouncing and/ore exporting will produce exactly the same results, frozen or unfrozen
 

3) If a track is frozen, I will feel discouraged from making edits to it (since I'd have to unfreeze, edit, refreeze each time).

I see this as an advantage rather than a disadvantage
 

4) If I want to copy sections of a frozen track to other parts of the song, I have to worry about fade in/out in order to avoid pops and clicks.

If you're talking about Midi tracks and their associated vsti, this should not happen
 
Do those disadvantages still persist in the current version of Sonar?  Or has working with frozen tracks become easier in later versions?




Don't forget, you can just as easily freeze a soft synth yet still be able to use your full range of mixing tools, Fx Bin, Pro Channel etc without having to unfreeze

I couldn't find a "disconnect" button in the synth rack, but I did see a "M"ute button.  I clicked on it, and noticed that both the drum instrument track and all the drum MIDI tracks were muted.  That made me realize that all I have to do is mute the drum MIDI tracks to prevent Drumlab from having anything to do.
 
When I run Sonar with all the drum MIDI tracks muted, I didn't encounter any problems.  I tested for about half an hour.
 
I then unmuted the drum MIDI tracks, and within a few minutes the sound died again.
 
I restarted Sonar, muted the drum tracks, and everything was fine.... until I unmuted them again, after which the sound died again.
 
This makes me suspect that Drumlab is somehow either buggy itself, or overloading SONAR and/or the ASIO driver.
 
Anyway, I managed to limp my way through a final mix, so I didn't have to bother with freezing the drum tracks.
 
For the next song, I will simply avoid using Drumlab!