I'd guess a small burr on the bridge saddle. How about a bit of steel wool or sandpaper to smooth it over? (Jon or Tommy should be able to give you a better suggestion.)
Sorry - just arrived in Southern Germany after some seriously long travel.
Bridge is a vintage trem on a Axis SS. One broke completely on a gig right in the middle of the "solo" on Higher. About died laughing when my singer get looking back with that - "why does this sound like crap" look on his face.