Sounds very strange. I replaced my front brake switch as it had stopped working properly. It was a simple replacement, and plug and play. I also ride an 05 1300R. Wish I could be of more help if you already said the wires were good. If there are two wires that run to it, no possibility they are installed on the wrong terminal? Not sure if they could get crossed, or if it would matter if they did.
I guess the only other thing could be if you have confirmed you have a proper and correct switch. Not sure how universal the front brake lever switch is with other bikes, but if it's a proper one for the VTX set up. I took my old one with me when I went and got a new one and found one that was nearly identical in appearance. All the mounting holes were in the right spots.
Otherwise, you may need to consult a wiring diagram and make sure everything is going where it should be. Did you mess with any other wires from the front brake lever to the brake light? Sounds very strange for a little piece to cause such grief.
I guess the only other thing could be if you have confirmed you have a proper and correct switch. Not sure how universal the front brake lever switch is with other bikes, but if it's a proper one for the VTX set up. I took my old one with me when I went and got a new one and found one that was nearly identical in appearance. All the mounting holes were in the right spots.
Otherwise, you may need to consult a wiring diagram and make sure everything is going where it should be. Did you mess with any other wires from the front brake lever to the brake light? Sounds very strange for a little piece to cause such grief.