If the machine is rebooting, check to make sure the processor is seated correctly against the cooling fan. Overheating from a cooler that isn't seated well on the processor will cause rebooting.

Folks, keep in mind that virtually all AV scanners have a kernel component also - used for real-time file scanning.  It is effectively a kernel-based driver.  If there is a BSOD or reboot happening during the VST scan, it will be worth temporarily disabling or removing your AV to see if the problem goes away.  The other alternative would be setting up an exclusion in your AV settings for the location of your VST files.
 
Noel can correct me if I'm wrong, but I doubt Sonar does anything directly at the kernel level, so can't reboot your PC.  However, it may be exercising something that does.
 
Question:  Does your CPU usage go up very high during the VST scan?

I appreciate your taking the time to respond to this thread.
 
But . . .
 

JonD
I would start by making sure the Fast Track Ultra is showing correctly under driver settings.  IOW, don't assume nothing has changed from your last setup.

From my second post to this thread: "It did not crash because of the interface or the OS. . . "
 

 After the upgrade, my interface changed to a generic ASIO driver, with the proper ones visible below but grayed out.  Once I switched to WASAPI (instead of ASIO), the normal drivers were accessible again, and I just manually unticked "generic" and ticked the correct ASIO drivers.  After hitting apply, this affected a bunch of other settings as well.

That has nothing to do with the problem that I experienced.
 

If your interface driver looks okay, then I'd move on to the plugins.  Try one or more of these:
 
- Under Edit-pref, uncheck "Replace VST2 Plug-ins When Opening Projects".  Apply.  Go back in and rescan plugins.  What happens?
- Under same place, uncheck "Rescan failed plugins"  Apply.  Go back and rescan.. What happens?
- If scans okay after doing the above, check the excluded plugins list.  Is Ozone there?

From my first post in this thread:
 
"After installation (an upgrade from X2), none of my VST3s showed up, nor did some VST2s.  I tried the "Reset and rescreen" trick recommended by Cakewalk, but that didn't work either.  Worse, Sonar crashed a couple of times in the process, usually when I tried to use the plug-in manager for scanning."
 

- Use shift key to open Sonar in safe mode (bypasses plugins).  What happens?

As the problem I'm having is that X3 is not loading VSTs, what in the world would this accomplish?
 

Point being, if it is a plugin causing a problem, you can isolate it, then once you are sure everything else scans okay, you troubleshoot the plugin (Make sure you have the latest version, or you may need to reinstall it, etc).

Point being, it is not a plugin causing the problem, as my later experiment with my laptop (also documented in this thread) established.
 
I've found a kluge to work around X3's failure to recognize specific VST3s.  However, I'm particularly concerned with the non-BSD, complete and total crash of the computer when trying to save the X3 plugin from Plug-in Manager with Sonar X3 open.  I also noticed some truly bizarre behavior of X3 that I haven't mentioned yet.  Specifically, at one of my re-scan attempts, it get caught in some kind of loop and kept rescanning the same VSTs, over and over again, and never finished.  The only way to deal with it was to kill the vstscan process.
 
My guess is that the Ubercrash was the result of the vstscan process running while I was trying to save the X3 preset.  My bet is that, rather than use standard OS calls for disk reads or writes, the software tries to go direct to the drive driver (or, maybe, a BIOS call); given the new "background scan" feature in X3, I'd say this is very likely.  I have a 512 GB SSD for a program drive and 4-disk RAID5 array for music data.  Though there is nothing particularly arcane about this hardware, I doubt either or, particularly, the combination are found in the typical Sonar user's computer.  The fact that I could save the preset on my laptop without crashing strongly suggests that I'm right about this, i.e. the problem is Sonar's write-disk coding, which doesn't play well some disk device drivers.

Silicon Audio
Folks, keep in mind that virtually all AV scanners have a kernel component also - used for real-time file scanning.  It is effectively a kernel-based driver.  If there is a BSOD or reboot happening during the VST scan, it will be worth temporarily disabling or removing your AV to see if the problem goes away.  The other alternative would be setting up an exclusion in your AV settings for the location of your VST files.

That's an interesting possibility, given that Sonar uses some kind of background process for scanning for VSTs.  However, I will not use any software that requires disabling AV.  Ever.
 

Noel can correct me if I'm wrong, but I doubt Sonar does anything directly at the kernel level, so can't reboot your PC.  However, it may be exercising something that does.

That's possible.  However, given that the VST scan is a separate process, I'm not convinced that Sonar does not by-pass OS calls for disk I/O.
 

Question:  Does your CPU usage go up very high during the VST scan?

My CPU usage never goes very high, except when rendering video. :)
 

Middleman
If the machine is rebooting, check to make sure the processor is seated correctly against the cooling fan. Overheating from a cooler that isn't seated well on the processor will cause rebooting.

Any mis-seated hardware can cause seemingly random hard reboots.  However, my machine isn't "rebooting."  It rebooted only once when I tried to do a very specific task that is often invoked by sophisticated software by calling on a device driver (or possibly a BIOS routine), rather than an OS call.

Okay, problem solved through a kluge:
 
How to add VST3 plug-ins that Sonar X3 doesn't include in the plug-ins browser:
 
With no project open in X3, and with the plug-ins browser closed:
Open the Plug-in Manager.
Open the X3 Producer Effects pre-set.
Click on VST3 in the left-hand column.  You should see the unlisted plug-ins.
Choose a folder in the far-right column (the pre-set column) and click on it to highlight.
Highlight the VST3 plug-ins you want to place in that folder.
Click on the "Add" button.
Click "Close."
The plug-in manager will ask you if you want to save the preset.  Click "Yes."
It will open a Program Manager window.  Save it as "X3 Producer Effects."
Program Manager will ask you if you want to overwrite the existing copy.
Click on "Yes."
 
That's it.  The missing VST3 will now show up in the Plug-in Browser window in the folder you chose.

[Edit: If you solved it, never mind...]

I have ozone 5 and Melodyne and X2 installed, etc. No issues with any of the stuff you are experiencing. X3 put ALL the VST3's where they should be, categorized them, etc.
So I do not understand how it can be X3. I didn't post to argue-just sayin.........
 
I am glad you found a work around.

Something weird obviously happened during your initial scan of plugins.  Anti-virus conflict maybe?
 
In any case, you seem okay with your "kludge" workaround, so congratulations!
 
Hardly the "VST Disaster" you proclaimed in your thread title.  Obviously up to you, but you might consider changing the thread name, so people perusing the forum don't get the wrong idea.
 
 

JonD
Something weird obviously happened during your initial scan of plugins.  Anti-virus conflict maybe?

Maybe.  It's still a problem.
 

In any case, you seem okay with your "kludge" workaround, so congratulations!

Congratulations for making the program work the way it's supposed to?  Okay.
 

Hardly the "VST Disaster" you proclaimed in your thread title.  Obviously up to you, but you might consider changing the thread name, so people perusing the forum don't get the wrong idea.

Until X3, I used Sonar tracking music, Audition CS6 for tracking vocals, and Audition 3.0 for mixing and mastering.  I upgraded to X3 because of the comp lanes and VST3 support -- I'm hoping to use X3 for tracking music and vocals, and also mixing and mastering, one program instead of three.  I use Ozone for mastering.  For me, the upgrade would have been a disaster if I couldn't get Ozone to work with it.  Given that VST3 support and comp lanes are two major selling points for the upgrade, yes, it would have been a disaster if these tools didn't work for me.  So, no, I have no intention of changing the title of this thread.  I'm glad I got Ozone working, but it shouldn't take a kludge* to do it, and the program shouldn't crash my computer when using it as intended.
 
 
 
*kludge  [klooj]  
noun Computer Slang.a software or hardware configuration that, while inelegant, inefficient, clumsy, or patched together,succeeds in solving a specific problem or performing a particular task.