Communication lost

[Skehtb]

Every time we drive our robot, it suddenly stops moving and the communication sign on the computer (the one that tells if there is communication between the robot and the computer) turns red. It only happens when we are activating the drive train - "moving" (4 CIM motors). When we shoot, collect balls and any other thing except for drive - it doesn't happen!
I hope you understand the problem, we realy need your help (off-sesason event in 3 weeks!)

Thanks!!