This was discussed and tested extensively over on TGP. Believe it or not, the strongest repair aside from threaded inserts is to simply put toothpicks and wood glue into the hole and tighten the screw while the glue is still wet. Don't worry, it won't glue the screw in place since wood glue wont adhere to metal but it does allow the pieces of toothpick to pack tightly into the threads and be glued in place.