a crack can turn into a split, and then the edge can separate from the ski. the best thing to do is send them back on warranty (if possible) or to file the crack out. if u have a crack that runs half ways thru the depth of the edge just file down a little farther than the depth of the crack and u shoud be ok unless it cracks where u have filed down. at which point u would need new skis.
Ice, snow, man-made, slush, powder, as long as u land on your feet nothing else matters