Is your Corbin hard? The only one I ever rode was back in '02 or '03 and I rode with it on my Connie for about 200 miles. It was really, really heavy, and EXTREMELY hard. People have always said that the Connie was a "buzzy" bike and I did occasionally notice some buzziness through the grips and the pegs, but the only time I ever noticed through the saddle was when I used that Corbin. By the time we finished the last 60 mile leg, my "manly" parts were asleep.
I hope this one keeps working for you!