I know exactly what bolt your talking about. Ive had a run in with this very same problem and i acually got lucky. I just droped down a size from the torx socket and went to a 6 point socket. It was a MAC socket and they have built into every socket engineering that helps with rounded bolts. I know that where this bolt is you cant get any cutting devices or a pair of vise grips. Bumer huh but try to drop to a 6 sided socket that fits tight and be strong and slow about putting torque on it. OH and the heat thing does help alot. Get one of those little MAPP gas torches from homedepot they work the best.