I noticed that if I plug in my Real Tone Cable before launching Rocksmith it crashes, but if I plug it in after starting up, it works. This is with the stock version.
I also noticed that my Logitech Webcam being plugged in will also cause the same crash.
To be clear, Rocksmith works fine so long as I have both unplugged when I launch.
I can then plug in the Real Tone Cable after it launches with no problems.

Thought I would share for inclusion in the troubleshooting journey and wonder if anyone has found a fix for this.
Otherwise this is a very low-lift fix.

In Windows Control Panel, under system sounds, I disabled all playback and recording devices except for the ones I was using to play rocksmith, and this issue was fixed. Seems like some audio playback or recording devices can cause conflicts with Rocksmith at startup.