I had problem with that bolt too. some one had tryed to take it out and rounded it. There is an quite easy solution if you have access to a welding torch(asetylen,oxygen) Take a smal nozzle(80L or 100L) and heat the bolt up until the head is dark red. Then you use a centerpunch or a smal tisel, and tap the bolt gently anti clock wise to open it. It might work without heating as well, but usualy you don´t have to hit it so hard if it´s heated up.
Places to be and things to do, see you all out there!!