michael japan
UPDATE--after editing, adding envelopes, fades, nodes, tweaking plug-in's --if--after pushing play, if I move the mouse around in the clips area or in the the area to the left that holds all your busses/tracks/plug-in names (what's that called? I've only been using Cakewalk since Cakewalk 3 --you'd think I would know) I digress--SO, if I put the mouse back in the toolbar and click before hitting play, then it doesn't do it-stable as my Golden Retriever's love. I can live with that. I do have to face the problem of adding strings now. With all the wav plug-ins in I get terrible latency. Can you fix that? No stutter, just a delay. Probably using about 20 of them. I guess I'll export the mix and bring it in as a stereo wav, bypass the plug-ins, record the strings, delete the mix, enable the plug-ins and do the final.  (or push PDC or bypass the plug-ins and play to a lopsided mix).Would love for you to hear the song. Doing an online collaboration with an artist in Austin Texas from Tokyo.Thanks for the help.
 
bumped up to 1024 and smooth.

If it is fine at higher latency it means that hit testing the clips view area is putting too much load on one of your cores that is used by the UI. Since that same core is in use by the audio engine its probably overloading at low latency and causing glitches. At higher latency the load is lower and so it doesn't overload. Bottom line is an excess load on even one core can upset the load balancing and cause glitches when you are running at super low latency. While editing its normally recommended to not run at low latency for these reasons. A moderate latency like 1024 samples should be fine.
 
That said if you can make your project available somewhere to download we can take a look and see if there is something that can be optimized better to alleviate such glitches.
 
Regarding the latency with plugins there is nothing we can do to prevent it. If plugins have delay, SONAR's PDC needs to delay other tracks to keep your audio in sync so its normal. Don't track with such plugins active as far as possible.

Noel Borthwick [Cakewalk]
If it is fine at higher latency it means that hit testing the clips view area is putting too much load on one of your cores that is used by the UI. Since that same core is in use by the audio engine its probably overloading at low latency and causing glitches.

I have the same issue, and I have some questions.
My config is old q6600 CPU and Focusrite Scarlett 8i6. Usually I work with 3ms ASIO buffer setting (Focusrite have this setting not in conventional way, as I understand it is 133 samples buffer).  I try to keep it small, but if CPU is overloaded, I increase it. The problem is that sometimes it start glitching (if I do recording of output, it is 50-100 intervals of zeroed samples). It happens mostly when I scroll Track View, or more annoying, when I move plug-ins sliders and knobs, but it could happen when just playing and not touching GUI, but very rarely. The strange thing is that CPU cores loading is 60-70%, and could never reach even 80%, both in Sonar Performance monitor and Windows Performance monitor, but glitches is still there. Is it the same CPU overload problem, but monitor just doesn't show loading right? Or could it be something else?