I'm not knocking it at all, I've also used it successfully before, just learning its use, limitations, and consequences of going outside the box (the hard way I guess :), and the value of reading help files first, I definitely learned my lesson, LOL, and was perhaps using it an unconventional way. If trying to reproduce Id suggest wearing hearing protection, or turn powered monitors or headphones way down. I guess the main issue is this seemed to somehow override manually shutting off audio engine, which I believe was my first reaction, and/or the main fader off first then audio engine icon, lastly I turned off audio interface to stop noise, so it seemed to somehow direct my audio interface to maximum output level, independent from Sonar setting. Noting I was somewhat in panic mode all occurring within a small number of seconds, I didn't wait to see if it subsided eventually.
It may be also that I'm pushing the limits of my processor on this project as well, and from some of the comments seems you need to really isolate the tracks from any other FX processing while doing this. I've had similar things happening using Nectar 2 as well, it seems to need maximum latency and really hogs processor, but it usually shuts down the audio engine, or I can shut it off manually without resorting to turning off audio interface.