Rostock movement issues

I've just recently completed enough of my Rostock so that I can get it moving. I'm using the Marlin firmware, `deltabot` branch. I plugged in my motors, turned it on, and hit "home" on Pronterface... *ChukkaChukkaChukka* it started moving off to one side, very jerkily. Only the motor plugged into the "Z" port on my RAMBo was making any appreciable movement; the other two were stuttering around without moving far from their original positions.

When I swap the motors, whichever one is plugged into the "Z" port works while the other two stutter in place. Any ideas as to what might be the issue?

I'm totally guessing at how to configure/upload the software as there seems to be no solid instructions anywhere!

Check whether your steps per unit are not too high. If they would be then the board would try to drive steppers too fast which can look like what you are describing. Maybe the carriage on z-tower can move a bit more easily so it is still able to move.