I am installing lights and outlets on my deck. I have a new sub panel with GFCI breakers. I ran a 12/3 line from the sub panel using 2 breakers. 1 line is for my hot tub and is working just fine. I just ran a single outlet and 2 light flood light off of the second hot line. The circuit goes thru the outlet and then to a switch for the flood lights. Everything is fine until I try to turn the lights on. Then the breaker trips. If I disconnect the light fixture ( a standard wet location 2 light setup) there is no problem. The outlet works and the light switch can be turned on (which should indicate that the wiring is ok). I have tried another fixture with the same results). All of the grounds are connected. The light fixture does not have a seperate ground wire. Does this sound familiar?