Or perhaps something else going on?
 
I fired up my studio machine yesterday to do some recording, but my video card suddenly took a dump. I happened to have an older card that tossed in to get the machine running. Everything seemed fine except Sonar. There was suddenly latency on the same project I've been working on that has been perfect in that respect.
 
Would a change in video cards cause that? I went from a Radeon to a GeForce. I think the GeForce has a little less RAM than the Radeon did.
 
Also, in prefernces I didn;t have the option to adjust the buffers. It was grayed out.

The other day my desktop went 'big', i.e. much lower resolution. This was immediately followed by an automatic Windows 10 update.  I let the update carry on, restarted etc. and the resolution was still screwed and display preferences didn't even show the high res I usually have available.
I suppressed the panic urge and as a shot in the dark I rolled back the display driver - and all was well!  I can't escape the conclusion that the Windows update was the culprit, taking place as it did two or three seconds after the display went wrong.

Well - As I recall yesterday Windows 10 updated my video driver (I have Windows 10 Pro, so I immediately made a new policy with the Local Group Policy Editor to exclude my hardware drivers from auto-update).
 
It is possible that you got that update too, and it broke compatibility for your older card. It is also fully possible that some other drivers are updated on your machine too. Sigh - Auto driver update - Another nuisance from Windows 10.

Interesting... I have been having issues with the displays for a while. I have dual monitors and all of a sudden a couple of months ago I would have to login from a blank screen only to have to restart in order for windows to see the main monitor.
 
Last night everything went "big" on me too, but I couldn't get it to act right no matter what I did. I think the card was just going bad and it finally died. Maybe that update pushed it over the edge. Windows wouldn't even see it as anything but a default windows display.
 
When I went to take it out it was too hot to touch. The older GeForce seems fine so for and when the machine boots everything is back to normal.
 
Still kind of odd I couldn't change buffer settings in Sonar, though.

I would not let Windows Updates touch any of my hardware's drivers with a ten foot barge pole.  Any drivers I would update manually - and from the manufacturer's website - never Microsoft's.  I have left Windows 10 security updates enabled but I have not allowed driver updates via Windows updates.

If Windows updates were to ever break Sonar - it would be due to a borked driver update via Microsoft.

Time to turn them Win10 updates off, I turned mine off around a month ago!
Not looking back! if it's not broken it don't need to be fixed.
All is working fine.. but I am wondering about the next generation of wave's plugin updates! 
Maybe Windows Anti-Kreater will be out by then. :) lol

Windows 10 update broke my radeon driver on my internet computer.
I went to the Radeon driver download page and updated the driver and all is well.
 

Wow! I can't believe how many people have been troubled by this same issue.
 
Definitely time to kill the automatic updates!

Make sure that Sonar is still using the correct audio device. It sounds like it may have switched to the HD Audio driver on the video card.

How do you turn off the updates in Windows 10?