NXT shuts down USB on Mac after connecting motors
The clicking mode means that you need to reload the firmware on the NXT (under the Tools menu in the NXT software).

If you still get the overcurrent shutdown using different cables and different computers, then the conclusion has to be that there is something wrong with the NXT itself. The USB port should be drawing little to no current at all since the NXT has its own power source.

It would also be worth contacting LEGO support if you do indeed have a defective NXT.