Two M's for a change!

Hey guys got a quick problem. I recently pulled a mamba maxx out of a box, plugged it in calibrated lights arm fine and then the truck jitters forward to reverse really quickly and repeatedly. Can someone tell me what this is?
I am running (or attempting to run) in reversing brushed mode. I am using a 6 cell pack. I emailed castle and was told to make sure the speed control was setup for brushed. Well when I ordered it, it was set to brushed (ordered it from a store online that sets it). This is the first time I tried to use it also.
I am hoping one of you will tell me it is a simple problem thats easily solved. I dont wanna go through castle because I bet there swamped with all the magic lamps there selling. Oh yeah and I cant program it on my pc because I have 64 bit vista as my OS. I looked through the book for manual setup but all I saw was how to wire it. I may have missed it but I didnt see it. Help is appreciated greatly as I need something too bash.

Brendan,