Well - if you go back to Lawp's question of 2 weeks ago, it turns out I think he had the answer.
It turns out, at least in my installation, Microtonic is set up by default to send MIDI out.
I turned off MIDI out in each instance of Microtonic, and have been running 5 instances of Microtonic for the past 8+ minutes without a hiccup. Microtonic is the only thing in this project, which would have definitely resulted in a crash previously.
(To turn it off, go to MIDI Config from the Main Menu in Microtonic, then deselect "Pattern Engine Sends MIDI Notes")
I only ever use Microtonic for its own on-board sounds, so doubt that the need to use it to trigger something else would ever be something I would use. I guess if you needed this, you would need to limit yourself to a single instance.
I know that in the past SONAR users have been critical of MIDI crosstalk errors - not sure this is a remnant of some of those issues, or a quirk in Microtonic.
2:43AM - please give this a try and let me know how/whether it works for you.
 
 
 

Well, son of a...
 
Yep, Lawp had the answer...but he could have phrased it like an answer! 
 
I didn't even know Microtonic sent out MIDI data. What a hidden nuisance! I will email the developer our findings. Now, if I can only make it the default to keep the "pattern engine from sending MIDI" turned OFF when adding new instances of Microtonic.
 
As I finish typing this post, 10 instances of Microtonic have been simultaneously playing with no errors or crashes for the last 13 minutes and 27 seconds!
 
BRAVO! VERY DESERVING OF A RUDY HARD-CLAP! THANK YOU VERY MUCH!!!

glad you found it; i didn't know microtonic put midi out which is why i asked; the bug is true for multiple VST that send MIDI out - if they happen to send midi at the same time sonar goes bye-bye; you can test this with 2 instances of jamstix, catayana, kirnu cream, etc - any that send midi out; cake know about it, for a while now

Well done lawp- good call. 2:43AM - glad you got the problem sorted. I also hope Magnus fixes this to allow you to disable this option as as a default. Even more, Cake needs to fix the MIDI cross-talk bug- it's been going on for far too long.
Cheers

Brando
Well done lawp- good call. 2:43AM - glad you got the problem sorted. I also hope Magnus fixes this to allow you to disable this option as as a default. Even more, Cake needs to fix the MIDI cross-talk bug- it's been going on for far too long.

Ah, it can indeed be saved for default.  In the MIDI config menu, there is a button to the right called Make Default. Disable "Pattern engine sends MIDI notes" and click this button. Subsequent loads of Microtonic will have the feature properly disabled... at least proper for Sonar!

Well that's good to know- thanks 2:43AM - Magnus is a great developer. How are you liking Permut8 so far? I also have Bitspeek which is fun but haven't bitten on Synplant yet. Eventually. Their 'Patternarium' for Microtonic is genius.
Thanks for finding this-

Brando
Well that's good to know- thanks 2:43AM - Magnus is a great developer. How are you liking Permut8 so far? I also have Bitspeek which is fun but haven't bitten on Synplant yet. Eventually. Their 'Patternarium' for Microtonic is genius.
Thanks for finding this-

Yes, Patternarium is pretty sweet. However, I find that most patterns and beats created are too complex for overall usability. It is, however, a great source for inspiration and offers a drum-sound buffet, which allows you to pick and choose from the various examples to build your own "kit."
 
I am demoing Permut8 now. I like what it can do, but programming is a bit (no pun intended) of a pain. For $60, I may pick it up anyway. I bought Synplant as a combo deal with Microtonic. Synplant is very lightweight, and it has a cool interface, offering a unique approach at patch generation. However, i find creating a good sound is pretty random, maybe a little too random. You can tweak seed DNA, but who the hell wants to do that?!?
 
It can create some cool, new sounds, however.