I would not ask about the failed search during the interview.
You could do some behind-the-scenes research (even last year's wiki or discussion boards, or asking for specific info on this year's discussion board). I know of one failed search from last year, which did not have anything to do with the school but rather due to the candidate's personal situation. It could be that the top candidate took too long to turn them down, and the other candidates accepted positions elsewhere in the meantime. That is, it might not have anything to do with the school or department.
I would recommend going into the interview with an open mind, but if your spidey sense goes off and you detect some dysfunction, then you might want to ask some more questions if you get an offer. Then you may be able to ask the faculty member who mentioned the failed search in the first place.