Hey Folks;
I was all spun about because I could not engage USB Debugging,
While I had Acer support on the phone for the Iconia 10 inch tablet, I remembered that I had put this tablet, for my mother, into EASY MODE....
perhaps the developers broke USB Debugging for when it is in EASY MODE because what person who needs EASY MODE would want to do anything with the operating system.
so I turned off EASY MODE, went back to developer options and Boom! no longer greyed out.
naturally I told the support person, in case they ran into this.
watch out of EASY MODE, it makes a screen easier for an older person, or a baby but it makes things harder for a support person.
enjoy