I've heard that calipers freeze when the "pins" lack grease, is the pin the bolt that secures the caliper? Or is it the tube inside the rubber boot that the bolt goes through??

 

the freezing of the caliper has to do with how the plungers release, and the caliper doesnt slide back to center, so it would be the pin lacking lubrication, i think.
-Patrick

 

when calipers freeze the piston(s) stop moving in thier bore(s), they have nothing to do with and it is very unlikely that they could be affected by the slide pins. the guide pins however as you are referring can get dirty,rusty whatever and either freeze or restrict motion for proper braking, if that is indeed the case take them off and lube them with white grease. you don't have to get in the tubes or anything just remove the pin/bolts lube the shafts with a light coat (keyword here as these are brakes)and look for any deep scratches or gouges.