First time poster but frequent listener of Car Talk. I have a question that I hope that I can get a little help. I have a 2002 Hyundai Accent with 147,000 miles. I live in Miami, Fl. I took my car to a national car repair company in March, 2011 because the wheel bearing (left) and CV axles (right and left) needed to be replaced. When the repairman completed the repairs, he failed to place the backing pin (?) back into its proper place. So when I drove, it made this grinding, scraping sound. I took my car back to the mechanic three days later and they fixed that problem. Within less than a week, I began having problems with the car shaking and vibrating when I was on the highway and while I was stopped at the light. When I took the car back for an assessment, thye informed me that the rotor was bad. When I asked him if the problems had anything to do with the failure of the repairman to place the backing pin in its proper place. He denied that the problems were related and tried to blame it on another mechanic. Approximately six months prior to getting these repairs done, I had my brakes repaired by a different mechanic. At that time, my mechanic did not mention any problems related to needing to repair the rotor.