Personally, I would take off the pad and inspect it. I'll speculate that a small chunk of the "forward" edge of the pad (read: as the disque "sees" it as the wheel spins) broke off the pad and it's now embedded in the pad further "back" (read: up), and eventually it will wear out/go away, but not before it may start a scratch. I had this happen to me (big time) on my first set of Cool Carbons that I tracked. Now I always take a file and chamfer the "leading" edge of the pad- maybe just 2 or 3 millimeters, and even the trailing edge somewhat.
http://www.google.no/m/search?site=i...amfer&sa=N#i=5