For christ sakes, whats with people using 12 point sockets to take off head bolts! Go get yourself a 6 sided hex one and whack it on with the hammer if need be, and hope there is still enough grip to take them out. And you should be working from the outside bolts, in if your not doing that already.
Stop using crap sockets and you won't have any of these problems. I remember having to use a break bar + extension to get enough torque to get my bolts out, and not a single stripped bolt.
Anyways good luck