disconnect the ballast from you lights and make sure none of the wires are touching each other then plug in the ballast....If the fuse pops then You ballast is more then likly Blown
sorry to have to say....But if the fuse doesn't pop then it's just happense to be how it is being wired!!!
__________________
500G Mixed Reef
__________________________________
Electrician, Electronics Technician, I can help with any electrical questions you might have!!
__________________________________
Kevin