BUMMER!!!!! There are ways you can do it. I dont think it is possible for you to fix the actual crack,you would have to feed a new sprinkler line under your driveway, which you can do or have a sprinkler company do it. If you decide to do it you should plan for at least 3 hours free! Let me know if you want to do it and ill gladly tell you the steps and what is involved!! Good luck!! P.S. are you sure that the leak is coming from under the driveway? it may just seem that way. Put on the zone and take a really close look!!
Thanks
Ray
Rays Above and Beyond Automatic Lawn Sprinklers