Anderton
Based on msmcleod's fix, they probably don't delete instrument tracks for a synth that's still in the rack. I don't, so I haven't had problems. Then again, I don't use Simple Instrument tracks, which may have something to do with my not having issues.

This could well be correct, I don't use 'simple instrument tracks' and haven't had any issues.
 
Additionally, I Googled 'NI Kontakt UI Problem' and found a number of forum posts describing the same error with alternative software including Logic Pro, Cubase and Ableton...
 
Logic Pro

 
Cubase

Anderton

sharke
Unfortunately though, as has happened to me many times before, Sonar has completely hosed the settings that I had in Strummed Acoustic. Back to square one!

I highly recommend saving any presets for plug-ins if you're not in the habit of rendering audio. I was checking out a lot of old projects lately to decide what to delete. There were, as expected, issues with trying to load 32-bit plug-ins into what is now a 64-bit system. However for those plug-ins where I had updated versions, so far all of them have been able to load any saved presets for the 32-bit plug-ins into the 64-bit plug-ins.

Yeah I've been doing that with the plugins that Sonar keeps forgetting my settings for. It's a complete PITA though, especially when you have to remember to save the preset again every time you make a little change. 

Songroom
Additionally, I Googled 'NI Kontakt UI Problem' and found a number of forum posts describing the same error with alternative software including Logic Pro, Cubase and Ableton...

 
For what it's worth, I can produce the Strummed Acoustic GUI problem in every DAW I somewhat regularly use - Cubase, Reaper, Sonar, Studio One, and Tracktion Waveform - simply by either not connecting output tracks to the Kontakt instance or by inactivating/bypassing the Kontakt instance before Strummed Acoustic is loaded. The GUI fixes itself when the plugin is activated and has its connections defined.
 
What's not clear to me, is why such a situation would occur when a synth is switched off and back on. (But if the related output tracks were meanwhile removed before the synth was switched back on, that would of course explain it.)

I should post this on the NI forum. It's good to know the fix. 
 
I guess my only problem now is synths coming out of hibernation with their settings garbled. For the life of me I cannot recreate the settings I had with Strummed Acoustic, it's lost the preset.  I've seen this on many occasions - memorable instances include NI's Rounds and Cakewalk's own Z3TA+2. My workflow with synths is to get the sound I want, print the audio and then turn the synth off in that state to preserve the patch. On some occasions, turning that synth back on later and feeding it the same MIDI resulted in wildly different audio than what I printed. This is taking into account any randomization in the patch (I'm not trying to achieve 100% nullable audio, just the same patch). In the case of Z3TA+2, it turned out that some of the LFO's had been reset. In the case of Rounds, it turned out that it's "progress" mode and voice mode had been reset to the defaults. I've also seen an instance of Waves Element come out of hibernation with factory default settings. Definitely an argument for always saving presets. 

sharke
I should post this on the NI forum. It's good to know the fix. 
 
I guess my only problem now is synths coming out of hibernation with their settings garbled. For the life of me I cannot recreate the settings I had with Strummed Acoustic, it's lost the preset.  I've seen this on many occasions - memorable instances include NI's Rounds and Cakewalk's own Z3TA+2. My workflow with synths is to get the sound I want, print the audio and then turn the synth off in that state to preserve the patch. On some occasions, turning that synth back on later and feeding it the same MIDI resulted in wildly different audio than what I printed. This is taking into account any randomization in the patch (I'm not trying to achieve 100% nullable audio, just the same patch). In the case of Z3TA+2, it turned out that some of the LFO's had been reset. In the case of Rounds, it turned out that it's "progress" mode and voice mode had been reset to the defaults. I've also seen an instance of Waves Element come out of hibernation with factory default settings. Definitely an argument for always saving presets. 

Hey Sharke - I want to send you a personal note - I've found your posts both helpful and informative over the years. My apologies for not clarifying my snarky post . It was certainly not intended for you - but was related to this post  " happens all the time to me.  maybe its for the best this product is now in the garbage... where it belongs."  That kind of crap gets me peeved. Cake hasn't been in business for 30 years creating garbage.  Again my snark was not intended to your posts  nor original thread start.  - but either way it's off topic to your legitimate issue and I was wrong to post it.

Rbh

sharke
I should post this on the NI forum. It's good to know the fix. 
 
I guess my only problem now is synths coming out of hibernation with their settings garbled. For the life of me I cannot recreate the settings I had with Strummed Acoustic, it's lost the preset.  I've seen this on many occasions - memorable instances include NI's Rounds and Cakewalk's own Z3TA+2. My workflow with synths is to get the sound I want, print the audio and then turn the synth off in that state to preserve the patch. On some occasions, turning that synth back on later and feeding it the same MIDI resulted in wildly different audio than what I printed. This is taking into account any randomization in the patch (I'm not trying to achieve 100% nullable audio, just the same patch). In the case of Z3TA+2, it turned out that some of the LFO's had been reset. In the case of Rounds, it turned out that it's "progress" mode and voice mode had been reset to the defaults. I've also seen an instance of Waves Element come out of hibernation with factory default settings. Definitely an argument for always saving presets. 

Hey Sharke - I want to send you a personal note - I've found your posts both helpful and informative over the years. My apologies for not clarifying my snarky post . It was certainly not intended for you - but was related to this post  " happens all the time to me.  maybe its for the best this product is now in the garbage... where it belongs."  That kind of crap gets me peeved. Cake hasn't been in business for 30 years creating garbage.  Again my snark was not intended to your posts  nor original thread start.  - but either way it's off topic to your legitimate issue and I was wrong to post it.

Fair enough, thanks for the clarification. 
 
Personally I think the full range of opinion has its place on the forum, everything from people who think Sonar is total garbage to those who think it's the bee's knees. I understand the sentiment of people who attack it with language like that - I've done it myself (although privately). If you're one of the ones who are lucky enough to have had a smooth run with Sonar then it's easy to think people are just trolling when they express their anger at the program - however if you've literally had your creative efforts thwarted time after time, spent hours dealing with problems and crashes instead of having a good time making music, and (like me) had hours of work repeatedly trashed by the program, then it's understandable to want to voice your frustrations and I think this forum is as good a place as any to do it. Also, when people lay into Sonar like that, they're not necessarily trashing Cakewalk's 30 year history, they're just trashing the program in its current iteration (big difference!)