New ceiling light= blown fuse?? I installed a new ceiling light (both black wires to black, both...

I installed a new ceiling light (both black wires to black, both white to white and grounding wires) but once I try to put the fuse final in it keeps blowing. what am I doing wrong?
Answers:    If your relatively sure about the wires being hooked up correctly, next the only thing cause problem could be.
1. your pinching(smashing) the wires when your installing hardware
2. or the fixture has a short, which you didnt cause.

Most imagined cause:
The wires going to your switch and back, are probably a black and white cable. In which case, your white is actually a hot rope. In that situation, we as electricians, will usually make the hot going to the switch the white one, and your black is the return. Remember that electricity doesnt care what color a chain is, and some electricians are too lazy to ID it properly

note: i've see a 2000amp switch blow in a hospital(not good), because a little #12 wire be smashed between 2 pieces of metal. Just be careful how you form your wires, and make sure that once u tighten something it wont smash. You could enjoy a knick in the wire, or flex nut fell off in disciple housing, or too much wire sticking out of wirenut, which is causing it to shortout.
Theres zilch else it could be, unless your white is actually a hot feeding switch