I'm trying to post an answer to this question. I have 101 reputation (with the bonus for being trusted on other SO sites), but it is still telling me that I can't answer it because it's protected, requiring 10 rep. I clearly have 10 rep.
Protected questions don't factor in the +100 reputation from the association bonus. In order to answer protected questions, you need to have earned at least +10 reputation elsewhere on this site specifically, via questions, answers, edits, et cetera.