RAMPS 1.4 to arduino connection hiccup

After uploading marlin firmware to my mega board, I plugged my ramps 1.4 in and added power to the ramps and the unit doesn't seem able to communicate with my Mac. After uploading marlin, I did test the just the mega with pronterface and everything was connecting and communicating well, but after attaching ramps there's no more connection. I checked my power supply(atx stolen from an old pc I had), and power is there so I'm at a loss as to where things are going wrong.
Any ideas on where the problem may lay?

There could be several reasons for this.

I can only talk about my own experience, I had a similar problem that was caused by a defective stepper driver.
Unplug your stepper drivers and check if the problem still exists...

I tried it without the stepper drivers or any other inputs and it was working, but an error message keeps popping up on my Mac that says the USB ports are drawing to much power and it shuts them off. The strange thing is the arduino board doesn't cause this error message by itself but when I plug the ramps board in it triggers it, but I have the ramps and arduino connect to the 12v and 5v power supplies so there really shouldn't be much current being drawn from the Mac. I'm no electrical engineer but my first thought is that I must have a short somewhere on the ramps board, but I have no idea how to figure out where the short is or isn't(if there is even a short).