One my end is on mono tracks. Change the track to stereo and all the noise stops. I discovered it when using Addictive drums using mono tracks with the console emulator on each track. With that many tracks the emulator was buzzing like crazy. I started troubleshooting the issue and discovered that changing the tracks to stereo completely eliminated the issue. Granted this is just a less than ideal workaround but at least this will quiet down your projects until Support comes up with a solution.

Just uncheck 64bit Double Precision Engine in Preferences.
 
This is what Cakewalk have suggested, and all these issues go away.
 
They are working on it.

John
See what happens when you go analog. 

OK, that was funny :-)
 
Thank you for posting the video of the issue. That is my exact problem and disabling the 64 bit option makes it go away but I don't have to restart Sonar. Just hit apply and the buzzing comes and goes.
 
I am glad it is being tracked down. 
 
Another fine example of the user base and Cakewalk working together :-)

I realize Cakewalk said they are working on fixing the problem, I just wanted to add that I also have a severe case of this problem with x3c. First thing I noticed when I loaded a project in Sonar after the x3c update was that loud, ugly buzzing/whining sound and quickly figured out it was coming from the CEs... and btw the buss CEs do it too on my end, as far as I can remember, but a lot quieter. You can make the buss CEs output the noisie louder by ramping up the input gain on the buss and pressing the tolerance button...
 
It would be very nice to have this fixed... Otherwise we have to untick 64bit double precision engine... or use x3b... or go back to Sonar x2

I realize Cakewalk said they are working on fixing the problem, I just wanted to add that I also have a severe case of this problem with x3c. First thing I noticed when I loaded a project in Sonar after the x3c update was that loud, ugly buzzing/whining sound and quickly figured out it was coming from the CEs... and btw the buss CEs do it too on my end, as far as I can remember, but a lot quieter. You can make the buss CEs output the noisie louder by ramping up the input gain on the buss and pressing the tolerance button...
 
It would be very nice to have this fixed... Otherwise we have to untick 64bit double precision engine... or use x3b... or go back to Sonar x2

Same here. When I turn the 64-bit engine off the buzzing stops, however there is still some weird behavior with the console emulator on mono tracks (the right meter is dead. I don't know if this is a graphic or an audible bug).
 
Today I discovered via a plugin that, when not playing anything, there is heavy activity not on the 2bus but on all the other hypothetical surround outputs (I don't have surround). I have a hunch this might be related. 
 
Looking forward to X3d! Problems aside, I have to say I'm greatly enjoying X3!

Yep, me too.  After the X3c update, I get the right meter of the CE pegged and a low level high pitched distorted buzz.  Never had it before. 
 
I did the VST rescan, no change.  I too find that un-ticking the 64 bit engine makes the pegging go away, but then the right side meter is dead.  Changing from mono to stereo does seem to cure the pegging, and the right side meter then responds correctly, but that's a rather odd workaround.
 
Please please please fix!  It's making projects un-listenable if they have CE (most all my recent ones do).  Any ideas? 

> Please please please fix!  It's making projects un-listenable
 
You made no mention that you disabled 64 bit precision engine. If you haven't there's your fix until X3D.

@CakeAlexS - Are you referring to my post?  I mentioned in the second section I disabled 64 bit engine and it made the right hand meter go dead, but did kill the buzz.

Appears you have since edited you post... OK thanks. If this is a different issue from the OP (I'm not sure) probably best to start a new thread.