If the allen heads are still there (haven't twisted off completely) this is the method i always use, and so far it's always worked.
Squirt RP90 or similar into the threads and give it time to work it's way in then find a torx slightly too large to fit into what's left of the allen hole, this is a torx head btw:
Hammer that fooker in there, all the way in, then get something on it with a reasonable length. Start the bolt with a jerking action (hit it with a hammer / palm of your hand if you're a tough bastard) rather than just constant pressure. It should brake any sticking of the threads and start you off. After you're done the torx is usually stuck in there pretty tight. Stick the bolt in a vice and tap the torx from the left, then the right and repeat until it comes out. Move onto the next bolt.
Good luck!
