Today, things worked amazingly well. I could work a couple of minutes with a particular project that´s usually haunted. After dropping the latency a bit and added a Melodyne region fx instance, the audio was replaced by the click. I check the event viewer it but didn´t find anything useful.
 
In the current project, the cpu load meters rarely move above 30% and never over 50%. When things are working fine, I can go down to 128bytes of audio buffer without any problems while the same project might give me the click issue even at a 2048 byte buffer.'
 
Another observation that probably makes the phenomena harder to pinpoint is that even if the probability of getting the problem (at least for me) seems to increase by the number of plugins I add, removing the plugins after getting the problem does NOT make things go back to normal.
 
Since I´ve seen this on two computers (Overclocked AMD 965BE & stock Xeon E3-1270), two OS´s (Win7 & Win10) , three audio adapters (Delta Audiophile 2496 PCI, RME Babyface & cheapo USB-adapter) & Sonar versions through X1 to current PLatinum, I´m having a hard time finding out what all these setups have in common, though there are some background services I´ve been using for many years.
While I have disabled them, I don´t know for sure if I really rebooted properly after doing so.

Some plugins and softsynths I use in most projects:
* Absynth
* Fabfilter Twin2
* FM8
* Massive
* Kick
* Kontakt
* Battery 3
* VAZ Modular
 
* Prochannel EQ
* Channel tools
* Melodyne
* Sonitus MOdulator
* Sonitus Compressor
* Sonitus Reverb
* Sonitus delay
* Ohmicide
 
My next step will be to uninstall/completely disable all background services & have another go.
 

The kick is iniated at measure 1, the rest at 2. Quite often, I tend to keep one or two silent measures in the beginning of each project.
 

57Gregy
Does your project(s) start at measure 1?

I haven´t had any CPU spikes so far, and when the problem is present Sonar seems to be running perfectly fine in terms of CPU load and screen updates. Only audio & VU meters would be affected. Unfortunately, nothing was to be found in the event viewer either.
 

Sir Les
It tells me OS management has corrupted ,or is tying things oddly together, causing the glitches...and IRQ and or interuptions of cpu and or Data transmittion is being hogged by unknown services running at times of heavy use, or exclusive use of resources.
 
I had cpu issues back in the day...Just open up sonar..and load nothing, do nothing..and watch the cpu metering and drive meters...for a bit of time..mostly a 20min run of nothing being done or more.
 
Is this showing usage beyond reason?...if the cpu meter suddenly spikes into the red?...can you capture a screenshot? save of ..and get the clocked time, and go into event viewer and read out what may be logged,and seek out what causes?.....i believe I did try to do this with MS tech support , costing a yearly payment plan to get someone who would...Yet each remote viewing viewer trying to resolve, would not go into event viewer at all...(until forced by me saying) He did nothing but sell me windows 8.1 to solve, which did nothing to solve for.....
 

No stretched audio. I´ve tried with and without 64-bit engine, no difference.
 

brundlefly
Any stretched audio in the project? Try disabling 64-bit Double Precision Engine in preferences; it can have issues with stretched audio, and possibly some plugins.

I disabled some background services and started Sonar after reboot: Teamviewer, Bitdefender & Dropbox. I could work approximately 10 minutes until the click thing happened so no luck there.
 

I've tried similar things to lv455 with no luck. It happens at least back to X2, and happens on Windows 7, 8, 8.1 and 10. It happens in projects with just Ozone (5, 6 or 7, VST2 or VST3) and Sonitus reverb. Stripping away most of the elements of a song (plugins, most audio) can leave it happening. It's flaky and sometimes when you think you've removed the culprit, it returns much later. I have a different audio interface to lv455 (Scarlett 8i6).

OK, I've got it happening with ALL tracks muted or archived except the Master bus. Output is set to none, so that should eliminate anything to do with audio drivers. Note the stats section of SPAN (which is on the Master bus prior to Ozone). The RMS display is corrupted (1.$), the peak values are -Inf, as are the max crest factors. The spectrum display is all green, meaning it's maxed out. I can change "Share drivers with other programs" without changing this, although if it is ticked, external audio files play without sounding garbled. Otherwise they do. What is going on here? I know others have occasionally had this problem (including Craig Anderton), but a few of us seem to suffer badly. 

I've had a somewhat similar issue which I've posted here: http://forum.cakewalk.com/2-issues-one-ongoing-re-placing-a-driver-on-bus-will-meltdown-audio-and-CPU-usage-m3495128.aspx
 
I've sent a couple of projects to Noel, who's looking into it. 
 
The horrible noise thing - overloaded high and low range distortion - occurs for me when I place a range of vst's on a bus...no specific vst but more often than not it's a compressor. As long as I turn the output down on my TotalMix and save the project, restart Sonar, it works fine and that plug-in never causes the issue again. If only occurs in the same project - sometimes - when I add another plug-in on another - or the same - bus. 
 
I don't remember how far back this started occurring. Maybe around the time I upgraded to Win 10? Just began to notice it started to regularly occur over the last 6 months or more. 

This happens for me too. It occurs when I close a project and open another one. Not every time, just occasionally. There is usually a blurting sound at some point during the project launch, but not particularly loud. Once the project is open, some of the meters, including the master bus, display full volume, although completely silent. Closing the project and reopening always cures it.

With my previous interface (Line6 UX2), the behaviour was slightly different. It normally occurred in the middle of editing a project rather than launching. Full-volume meters again, but this time indicating a dreadful whining sound. A re-boot was the only way to cure it.

I don't remember it ever happening in pre-X versions of Sonar. I believe it started for me in X2.

I've had this happen to me in the past and most recently with iZotope Neutron.  In the case of iZotope Neutron it was because the VS2 version of the plugin was loading by default.  The issue does NOT happen with the VS3 version.  In the past the issue was also caused by a plugin.  I think I would start there and really focus in on pinpointing which plugin is the culprit.