Maybe a short, or a loose wire, but really there are many things that can go wrong with electronics that I cannot diagnose it without seeing it. What I would do is to go through the whole installation again step-by-step (without actually cutting or soldering anything) and see if you might have soldered a wire to the wrong connector or anything else is out of place (I've done it myself a million times; last time I wired the wrong wires to the switch in my strat-copy so now when the switch is in the neck position the bridge pickup is active... but at least I got a tone control out of it)