so I thought this was maybe a problem with the cthulhu vst itself, but it looks like it's not...
insert 2 instances of cthulhu in sonar, enable midi output on both. insert an instance of dimension with a midi track set to receive midi out from instance one of cthulhu. insert rapture receiving midi out from cthulhu 2.  enable midi echo on dp and rap midi tracks. arm both for recording.  record.  dp and rap pick up input from both instances of cthulhu simultaneously. 
same thing happens with midi out from reaktor and kontakt. 
verified this is not a vst problem by following the same steps and routing using studio one and it works perfectly. 
 
attempted fix: make a copy of the cthulhu vst and give it a new name and insert that as instance 2 in sonar.  still no joy.  disable either instance's midi out capability and they record fine one track at a time in sonar...
 
happens in x1 as well... 
 
so, I guess my question is - does anybody know of a way to get two instances of a soft synth sending midi output working in sonar???
any help appreciated!
 
 

Not familiar with cthulu, but if you are sending midi out on omni ie to all midi channels from the softsynth, I would expect the outputs to be merged ie anything receiving on omni would receive and respond to both outputs. If you can send midi out from the softsynth on a single channel and set up the receiving synth to read just that channel, you might get it to work.  

they're going out on different channels and set to be received discretely by each midi track.  i tried reaktor in studio one with both instances sending out on channel one and each track received exactly what it was supposed to. :(

video of problem here... http://youtu.be/73Pf1b6bTk8

There is some history of misrouting midi from VST output. Some posts here and here have some discussion of it. I have not examined your video, so I don't know if it's a match.

Cakewalk fixed a bug they called "midi crosstalk" which involved the input from external controllers, but apparently did not fix the VST midi output problem (post here).

Thanks bvideo. I must say it's comforting waking up in the morning knowing I'm not alone in my suffering. 
Those were lively lively discussions! I hope this can be fixed because this is a almost a show-stopper for me - not just in sound design but in my development projects.  The only saving grace is that it's actually writing the correct controller numbers and midi channels (I'll have to do more work with midi notes because I'm only doing cc automation at this point) so I can work around it with midi filters and such, but still...
It's really too bad.... and I'm left to wonder now if this is why beatscape is no longer included in sonar (aside from beatscape's own long list of bugs).  AFAIK, beatscape was/is the only CW synth that sent midi output... maybe I'm wrong.  
I'm also left to wonder if since CW apparently fixed the multiple vst midi output crashing sonar bug (this hasn't killed X2 for me) if they think they fully resolved the problem. 
Think I'll drop SilkTone a line to see if he is still around or how Studio One is working out for him... 

Thanks for the references.

And it was a bit disappointing to see Zyler's response at the end of http://forum.cakewalk.com/tm.aspx?high=&m=2807089&mpage=1#2807418
"At this point, I think the thread has inarguably been solved: 
"MIDI Cross Talk fixed?"  If by MIDI Crosstalk you mean the ability to record from multiple hardware devices, yes.  If you mean the bug causing a crash with multiple VSTs sending MIDI out - no, but it will be.  I sincerely hope this helps. "

which came across as a bit dismissive and passive-aggressive, when the thread began by asking "Are multiple instances of Cantanya and Thesys possible now? " -- to me it was obvious that the thread had nothing to do with midi hardware.  really too bad, when this is the attitude of some people towards those keeping them employed.  just my 2c.

"You've thus far managed to elicit a response from Product Management, Product Marketing, and the CTO of the company - all of whom have acknowledged your issue and the fact that it must be fixed"


life on earth is beautiful.... :-)  four years since the bug report and counting...

i left earth a long time ago and landed on the planet forumstall-x... where all shall be acknowledged but never appeased.  
unfortunately for people using midi in creatively challenging ways that may be outside of the norm and developers  these are the kind of glaring *really - this doesn't work???* issues that makes the whole product start to look amateurish after a while.  very pretty but very amateurish.  i really hate saying that because it is so pretty after all... 

Hey, swamptooth, what channels show up in the events?

Bob Bone