I've noticed a lot of Sonar users seem to be having problems with their versions of Sonar. The fact that many of these are not versions linked to the Command Centre means that the problem has nothing to do with Sonar servers or the program itself. I suspect the problem is two fold:
 
1) Windows updates often cause problems with Drivers. 
 Every time there is a new Windows update I have to roll back the onboard drivers. This is not so hard to do.
 Right Click the Audio icon on the bottom right bar of computer.
 Select 'Solve Audio Problems' (I'm not 100% that is what it says in English as my OS is Italian)
 There are lots of resources out there if you google them, for example: http://www.ibtimes.co.uk/windows-10-how-fix-sound-issues-after-upgrade-1513693
 I suspect that in the majority of cases, audio and recording problems are due to drivers.
 
2) People are testing out alternative DAWs.
 Like eveyone else, I've been trying out the various demo versions of DAWs out there. So far I've tried: Presonus Studio One, Samplitude, Cubase, Waveform 8, Studio Bus, Mixbus, Mixcraft and Reaper.
 One thing that many people don't consider when installing these is 'conflicts'. For example, Steinberg installs their own 'low latency ASIO' drivers which can conflict with your other ASIO drivers. I've also seen it said that Reaper can take Exclusive control of your drivers which can create problems when you try to fire up Sonar.
 Furthermore, some VST paths can overwrite Sonar paths - if any bundles contain the same FX, there could be problems (especially if they are older versions overwriting newer versions). I had this problem when I tried reinstalling an older version of Sonar onto a machine that already had Sonar Platinum on it.
 Then there can be a problem of uninstalling demos.  Many DAWs leave bits and pieces behind. Some delete folders which are shared. Some delete FX that they installed, which could be the same FX as used in others.
 
 How can you avoid these problems?
 
1) Keep rolling back those drivers to the last functioning version. This may involve uninstalling them completely, restarting, and then searching for the drivers on your computer. Check out this link: http://www.intowindows.com/how-to-restore-previous-version-of-a-driver-in-windows-10/  Also, check the Properties of each audio device. Turn off Enhancements and sorround. Check the 'exclusive' rights of the device. Sweetwater has a good guide her: https://www.sweetwater.com/sweetcare/articles/resolving-audio-interface-issues-on-windows-10/ 
 
2) If possible, before installing any new DAW, make a backup or rollback point. It might also be good to take a snapshot of install paths (or write down all install paths) just in case you may have installed VSTs or Fx ins some obscure places. If you can, install demos on a seperate machine or drive. Make install paths exclusive and seperate from existing & functioning paths. Uninstall any demos that you don't need or use. If you have problems after uninstalling demos, try reinstalling your version of Sonar to repair broken or missing paths etc.. An alternative is to install any demo in 'sandbox' or 'virtualbox'. There's a guide here: https://lifehacker.com/how-to-safely-test-software-without-messing-up-your-sys-1680608496 and a list of sandbox apps here: http://www.thewindowsclub.com/sandbox-sandboxing-software . I must admit, I haven't tried this myself, but it might be an option.
 
Hopefully, this will avoid some of the problems being reported.
 
Now, back to doing some music....
 

There should be kind of special function in Windows like 'sealing driver' which would protect driver both against update from MS updates like other accidental sources  like 3-th party installation with side-effects: )

"Every time there is a new Windows update I have to roll back the onboard drivers."

You need to stop windows update from updating your drivers, or better still download the latest drivers from third party site and install. Windows update *may* leave them alone after after that.

"Keep rolling back those drivers to the last functioning version."

Sorry but that's a really bad thing to do. The only time you need to roll back drivers is if you have problems. You are much better off going to manufactures websites and downloading/installing the latest drivers.

All software has dependencies. When developers bring out new software it's generally tested with the latest OS, OS updates and programming libraries by default. After a while mixing older software with newer software tends to break things. So you either take your PC off the internet and just use old software (never install anything) or you try to keep everything up to date and take regular backups (recommend).

You can tell Windows 10 not to touch any hardware drivers with Windows updates.  I do all my driver updates manually by going to the manufacturer's websites rather than trusting Microsoft to deliver the right ones.

I agree that it's not the best advice to NOT update drivers, but I've noticed that Windows keeps automatically updating my laptop drivers to their own version, which always creates problems for me. As my laptop is not super new (I use a firewire interface, so I'm holding on to my old HP) the manufacturer has ceased updating the drivers for compatability with W10. Same goes for my Edirol Fa-101. Having the most up to date drivers is the best option if they are available, but when Windows install their generic ones, I have problems and roll back to the ones that worked.

burgerproduction
I agree that it's not the best advice to NOT update drivers, but I've noticed that Windows keeps automatically updating my laptop drivers to their own version, which always creates problems for me. As my laptop is not super new (I use a firewire interface, so I'm holding on to my old HP) the manufacturer has ceased updating the drivers for compatability with W10. Same goes for my Edirol Fa-101. Having the most up to date drivers is the best option if they are available, but when Windows install their generic ones, I have problems and roll back to the ones that worked.

https://www.laptopmag.com...ownloads-on-windows-10

I clicked on the link in burgerproduction's first post.  It said, "Step 3: Go to Advanced section and change the bit rate to either of the following: 24bit/44100 Hz or 24bit/192000Hz depending on the speaker configuration."
 
I tried to change mine, but it wouldn't allow me to.  Mine says 16-bit 48000Hz.  When I tried to change it to 24-bit 44100, it says it's not supported.  Is that normal?  My audio quality could be a little better.
 
Greg

Greg that is a windows on board sound chip settings and nothing to do with your Focusrite. I found a lot of bad information in that post, 
Rule # one- Don't believe  everything you read on the internet. 
You make all  driver settings in the Focusrite control panel. Not Windows audio panel. 
On board audio is normally 48 because of movies so a lot of on board audio is only 48. My old Sound Blaster was like that too. Focusrite supports from 44.1 up to 96 even higher on some models. 
If your audio doesn't sound good to you it will be your monitors, not 44.1. Many of us use 44.1 without issue. It makes it easier to produce CD's. 
 

burgerproduction
I've also seen it said that Reaper can take Exclusive control of your drivers which can create problems when you try to fire up Sonar.

It can also break your hard disk, permanently destroy your creativity and occasionally steal you music
 
Seriously... That is the only DAW with "portable" install option (it does not touch anything outside installation folder). And as any other program, it use the same set of APIs to work with audio drivers. I mean that is least intrusive DAW everyone can try without consequences, yet you mention it as a possible evil. It is not evil, it is Reaper
 
Can it happened that the sound is no longer working in Sonar (or other program) after you was running some other  program? After several years I still have not found any serious explanation for the effect, but the answer is YES!
I have observed than several times, with several interfaces, on different computers.
In theory, ASIO drivers should be most robust since that should be by definition most strait way between user application and hardware (bypassing any Windows stacks, and so dependency from them).
In practice, proprietary ASIO drivers fail as first. Why? As I wrote, I have not found any serious explanation.
Based on my experience, I have a guess:
when an application intentionally or unintentionally put the driver/hardware  into particular mode, it (or some part of it) is preserved inside the driver/hardware. With "Friendly" intention to restore the environment to the state which user has used the last time. But that can produce the "disaster", if that mode is buggy (for the driver/hardware combination), any attempt to restore it trigger some hangs inside hardware/driver. Sometimes it is possible to "overwrite" it from application / control panel / windows restart, sometimes by reinstalling drivers, in worse scenario by reinstalling Windows (I guess if the mode is saved in registry/ini files which are not cleaned during uninstall or some windows stack options is the root of the problem).
2 examples:
1) I had SB, M-Audio, usual build-in interfaces (HDMI, Realtek) and some extra "USB-Audio" (mixer, vocal processor, drums, etc). Everything was ok. M-Audio had own ASIO drivers.
Following one thread in this forum, I have started to "play" with ASIO drivers. Installed SB ASIO and ASIO4ALL. Everything still WAS normal at first. But then I was changing options to measure the latency, switching between devices and drivers. At some point something has "clicked" (not audible). After that, M-Audio could no longer work properly in ASIO. I had to increase ASIO buffer, but even than there was weird problems I was not experiencing before. I have uninstalled SB ASIO and ASIO4ALL. No change. Reinstalled M-Audio driver. No change. Only after next big Windows update (which has effectively re-installed windows behind the scene...) everything was normal again.
2) I was using VS-20 with my notebook, preparing for a "gig". Half a day things was smooth (I was disconnected from the Internet). But then one VST has crashed, taking the DAW and the driver with it. Reboot - no joy (windows audio OK, ASIO not available). Only re-installation of drivers has helped to bring ASIO back (obviously not acceptable for anything half-way serious or live).
My solution was to get most stable on Windows drivers... means RME. That can not guaranty no problems, but at least I am convinced if I observe something bad, that is not from the driver (there is no evidence RME has untested modes... probably the reason they do not allow lower then 48 buffer for Babyface, while other, to declire "ultra low latency" allow setting whatever, even in case that does not work at all or known to have problems).

azslow3

burgerproduction
I've also seen it said that Reaper can take Exclusive control of your drivers which can create problems when you try to fire up Sonar.

It can also break your hard disk, permanently destroy your creativity and occasionally steal you music
 
Seriously... That is the only DAW with "portable" install option (it does not touch anything outside installation folder). And as any other program, it use the same set of APIs to work with audio drivers. I mean that is least intrusive DAW everyone can try without consequences, yet you mention it as a possible evil. It is not evil, it is Reaper

And what's about all those "ReaRoute ASIO" drivers that reaper installs? After Reaper's installation I had first to disable all that **** in Sonar and enable my hardware ASIO drivers!