You could test this by driving the robot backwards. Instead of changing motors around try using this in your code.
Code:
Left_Wheel = (254-Left_Wheel)
Right_Wheel = (254-Right_Wheel)
Or you could just try driving with your joysticks backwards.
EDIT: It just occurred to me that our robot has drive wheels on the front and omnis on the back. Hope this won't be a problem.
__________________
Branden Ghena - Michigan Tech Student and Team 240 Alumnus
Working Towards: Electrical Engineering and Computer Engineering Double Major
"All we have to decide is what to do with the time that is given to us." - Gandalf