Character Controller going crazy

Hey, I'm a Unity noob and I've been going through the Hotshots book. I'm using the second 3rd person custom script they have you construct, and it works fine with their model. As soon as I attach mine, it goes nuts. He will randomly shoot really high into the air, and come down just to literally bounce and go straight back up, and his momentum NEVER stops when I CAN get him to walk right. I've made the model a child of an empty, and disabled all colliders for it leaving only the original FPS controller. He will keep walking up until I tilt the view downwards, then he falls. Any help would be greatly appreciated, and I'm willing to send the porject to anyone who thinks they might be able to help. Thank you in advance.