Your antenna resting in the DIN opening should not short out the radio; if it did for some reason, the fuse would blow. I would double and triple check your power and ground connections - particularly the ground - in fact, you said you grounded it through the factory harness - i would ground it directly to the chassis (or something directly connected to the chassis, such as the HU mounting assembly). Just find a bolt that's attached to something large and metal, sand down the surface to remove paint and dirt, connect the ground wire to a ring connector, and bolt it down. I think this will most likely solve your problem. Also be sure to check all the fuses; there might be one in a fuse box in addition to the one in the back of the HU.