Was this ever fixed?
I have the same problem. I had not removed the old drivers from my computer (just forgot), and plugged in the board yesterday for the first time in forever, and my computer crashed. I have not been able to get past the login progress bar for any user on the computer.
I removed usbserial.kext, renamed my Library/Extensions to something else, reset the RAM, tried logging in with shift, all the things they tell you to do - still no luck.
(To answer your question: naturally, I didn't leave the board plugged into my computer after the first crash.)
Please help. Thank you.