Did the cart run again after sitting and coolin down? If so chances are the controller went into thermal shutdown from over heating. Does the cart run now? If it does just make sure the connections are good everywhere and ride it a while and keep checking all the cables, motor, controller and forward/reverse switch for heat. I'd seriously think about changing all the cables to 2 guage. I know D&D has a couple motors that require 2 gauge if using a high amp controller. The doubling up on the cables is not the right way to fix your problem. Also all the cables should be the same size, so they all should have been doubled up if thats how the shop set the cart up.
Without knowing exactly what you have as far as motor, controller, I really don't know what else to reccomend. But like I said think about redoing all the cables and getting rid of the doubled cables.
Seeing how the cart is a 2007 and you bought it from a dealer with the addons installed by them I'd take it to the shop you bought it from and make them fix it.