I know IK Multimedia does that kind of noise thing. Might be a place to start if you're using anything by them.

Actually, I don't use much in the way of vsts. For my current project, an orchestral piece, here is what I'm using:
 
VSTi: 1 Play, 1 Aria, 1 Vienna, 1 Dim. Pro, 2 Kontakts with Cinematic Strings; 3 Studio Inst with Strings. All have just a handful of insts. on them.
 
vsts: 1 Spaces, 1 Sontius Compressor, 1 Tube Leveler.
 
The VSTi go to the Reverb bus, with Spaces. Spaces goes to the Mix bus, where the Compressor and Tube Leveler are.
 
That's it. Although sometimes I turn the LP64 EQ on, but usually I leave that for mastering.

You didn't seem to follow my instructions. When Troubleshooting one must use a process of elimination.  Jumping all over the place is a big waist of time. It's easy to pin point issues. 

One small step at a time - does it happen in exactly same place(s) every time you play back or does it appear randomly?

I asked that and seems he didn't answer and it is real important to those who are trying to help

Sorry! you're right, I need to provide more info, and try your suggestions.
 
First, it appears to be random. Hit or miss. Today on my run through my project, to see how what I did last night sounds, it didn't happen at all.
 
I will do the following to troubleshoot: the next time it happens I'll stop play there and note what synths and instruments were going. I'll do that every time I hear the noise. Hopefully, a pattern will emerge and I'll be able to zero in on the culprit.
 
I appreciate the help.

Freeze all tracks you aren't actively working on.
Does it still happen?
If yes, then it's something common (busses, masters) or perhaps even outside of Sonar.
 
If not, then:
 A.
Unfreeze half your tracks.
Does it still happen?
If yes, re-freeze half of the tracks you just unfroze.
If not, re-freeze and unfreeze the other half.
 Goto A.
 
Keep going, narrowing down by halves, until you are left with the track that's causing it.
 
Also, activate the waveform display on the master track(s) and
see if there's anything visible.
 

Why use Freeze? Muting should be sufficient.

I just had the noise. The only two synths playing were Dimension LE and Kontakt. Is it logical to think it might be one of those two, or one of the insts. on them? The Dim. LE only has a harp from Garrison Pocket Orchestra. The Kontakt has Cinematic Strings, with all 5 groups playing (violins1, violins2, violas, cellos and basses). The only fx are Spaces on the reverb bus and Sonitus Compressor on the Mix bus.
 
I'm using Dim LE because the full version won't insert, says it ay not have been installed correctly. Don't know if that is significant.
 
Will continue troubleshooting.

I beleieve Dim Pro needs you to activate by running as Administrator. 
 
OK, Random as said is real hard to pin down. 
 
What I was doing in the case of Sonar randomly crashing was keep a notebook and write down what was happening at the time of the crash. 
For a while I thought it was a 32 bit VST I was still using because it was in all projects that crashed. Then one day I had a crash without that VST so back to square one.
 
WHat seem to stop the crashes for me ( and others too) was to make sure and save A LOT.
Like every 10 little edits. The crashes have almost stopped since then with only once and guess what,, I hadn't saved for a long time while editing. 
 
You problem is different but sort of the same because Random is tricky. 
So start making notes. 
I would for sure try using different plug ins.