Thought I'd post this just to help out.
Recently I was working with two Pololu 18/7 simple motor controllers and the EZ-B. After some configuration with the Pololu software I got the controllers working with the EZ-B.
I decided to try to calibrate the left controller as it didn't feel like the right while I tested it in the servo panel. After getting it calibrated again, I plugged it back in to D12 while the power was still applied to both the motor controller and the EZ-B. Simple, or so I thought. I missed the pin orientation on the servo (Motor controller) plug and shorted positive to negative. The 5a I/O regulator let out a pop and a cloud of smoke. No more 5vdc at the servo pins. The included fuse didn't blow first.
I unsoldered the LM1084 regulator and without paying close attention, order replacements. Here's what I learned: The regulator is availabe in several forms all bearing the LM1084 prefix. If this happens to you, make sure you order the LM1084-5. I ordered 10 of the LM1084-adj. Big mistake!
I had to reorder the correct -5 designation so my bot sits and waits again.
I hope this helps someone out there if they have the same problem.