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.

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?

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.

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!