I won't usually read an author bio until after I've read a book. There isn't any real reason for this, except that I just don't think to read them. Usually what makes me flip to the back cover and read the blurb is something in the book that makes me wonder...where are they from? Have they always been an author, or did they have another career?
So, to actually answer the question, no I can't think of a specific instance that an author bio has turned me off or made me want to read everything they've written.
Do you have author's whose bios have turned you off on their books?