// set medium sized images to crop to dimensions in media manager
if(false === get_option(“medium_crop”)) {
add_option(“medium_crop”, “1”);
} else {
update_option(“medium_crop”, “1”);
}
http://stackoverflow.com/questions/3454337/crop-thumbnail-to-exact-dimensions-on-wordpress-for-medium-size
http://wordpress.org/support/topic/force-crop-to-medium-size