Found that my Win 10 upgrade defaulted me back to hiding some folders and file types. Deleted aud.ini but no help. Updated display, monitor, audio interface drivers. Still no fix. Will report back here once I go through tech support.
 
Thanks for the help...good folks here.
 

When you deleted aid.ini did you need to set up the audio interface settings in preferences again?

BTW if you are running asio4all remove it.

hey Dok.....no, when aud.ini is removed there is no need for me to set up audio device again. The device and all i/o seem to be picked up automatically when Sonar is brought up after a reboot. Otherwise, if I attempt to load an existing project which hangs Sonar and then exit out, if I restart Sonar without rebooting all audio device settings and i/o will be blank with Sonar warning there is no audio device.
 
Will look for/delete asio4all......thanks!!

When you started Sonar again after deleting aud.ini did anything happen at all when starting Sonar? If not I think you might have got the wrong aud.ini file. Ta.

nothing special happens when i delete aud.ini and restart Sonar. Absolutely no change in start-up behavior or otherwise. Sonar acts AOK and completely normal until I load an existing project which freezes it up ("Sonar is not responding"). Is there a way to load a project without activating the associated plugins? I've found that some existing 'minimal' projects will load and play in Sonar Platinum just fine, but most will freeze Sonar such that I can't tell what plugins are being used in these projects.

To start a project in "Safe Mode" hold the SHIFT key while loading the project.

Phone support should be open in about 40 minutes. Type up a ticket (if you haven't already) and give 'em a call.
 
Seriously you won't regret it. Also ask them to send you an email with details on the solutions they figured out so you can reference them (and they may come up with more stuff after you hang up).
 
They're really good at this crap and decent conversationalists too (unlike most tech/customer support drones... well and these dudes ain't drones).
 
Cheers.
 
Edit: I seriously think you're just gonna be chasing your tail here on the forum with this particular problem. Might as well just get it from the horse's mouth and get on with creating.

I don't think you deleted the correct AUD.INI if it was business as usual afterwards. At this stage I agree with Beep.

Dupe

Dok/Beep/scook....appreciate all your timely help. This problem was solved. It was a plug. Not sure whether it is misbehaving or a Sonar bug at this point. Found it through selective deduction loading project in safe mode many times. It's a GForce M-Tron Pro plugin. Contains many authentic samples of the original mellotron tapes. That's one I use a lot. 
 
I did go through tech support and tech was certainly nice enough. He remoted into my system and offered suggestion which i tried tonight, but didn't fix the issue. Really happy to be operational again. Now i need to catch up on the all the app changes that occurred since X3. Thanks again guys!