Yeah. What Andyrew said.
Also, you can try other traditional methods of freeing a bolt... heat (a torch), and tapping. That said,
I'm not comfortable with putting a torch to my calipers... it just doesn't give me a warm and fuzzy feeling.
I don't think my 33 year old calipers had ever been opened up. That's a lot of time for a bolt to become stuck.
Good luck, and let us know how it turns out.
-Rusty