Using some aluminum-grade anti-seize on those caliper mounting screw threads prevents this thread galling problem from happening. I've had really good luck with the aluminum paste formulation anti-seize for bolts like these - Permatex #81343 works great, and comes in an easy to use small tube which doesn't seem to evaporate, or allow the oil to separate from the solids.
Going for a light, even coating on the threads (so it looks like in the photo below) keeps things neat and tidy:
http://986forum.com/forums/performance-technical-chat/67401-how-properly-use-anti-seize.html#post545070
Threaded Mode
