possible grounding issue?!

[2rotor]

it sounds to me like your battery terminals on the cables suck, you didnt say if you cleaned the cable ends either (at the battery and chassis/motor), you just said the engine chassis had grounds and they were firmly connected.
also, have you tried bypassing the ignition switch to rule it out? maybe just putting a voltmeter on the terminals to make sure you have ~12v in and ~12v out where it should be.

[Master Shake]

it sounds to me like your battery terminals on the cables suck, you didnt say if you cleaned the cable ends either (at the battery and chassis/motor), you just said the engine chassis had grounds and they were firmly connected.
also, have you tried bypassing the ignition switch to rule it out? maybe just putting a voltmeter on the terminals to make sure you have ~12v in and ~12v out where it should be.

i did try cleaning the posts on the battery but it could be the connecting terminals, not really sure, so i'll get down the Advance and pick up some new ones. i think they're only like 5-10 bucks, so it shouldn't be to bad.