Can you insert anything behind the brake pad or is the entire surface frozen to the clamp? I've had a couple of stuck pads, but I've been able to get them out by either working something with a sharpish point into the pad material and just pushing (or hammering on the end of the handle) or by using a screwdriver as a lever between the pad and the back of the clamp.
A picture might be useful.
Winter riding is much less about badassery and much more about bundle-uppery. - malkin
1995 Kona Cinder Cone commuterFrankenbike/Selle Italia SLR Lady Gel Flow
2008 white Nakamura Summit Custom mtb/Terry Falcon X
2000 Schwinn Fastback Comp road bike/Specialized Jett