[cbhl]

Check all wiring is done properly. Also, I believe the DC controllers require the battery to be plugged into a particular set of battery terminals, although I'm not 100% sure -- you could try connecting the battery to the other set of battery terminals and seeing if it helps.

If you're using the new JoystickDriver.c and have the diagnostic info displayed, you should be seeing the battery voltage as Ext Batt -- it should be around 12 V if your battery is freshly charged. A lower value would likely indicate a loose cable or something.

Finally, if you don't have the encoders set up, make sure that you uncheck "PID Control" in the Motor/Servo/Sensor setup dialog in RobotC -- if I recall correctly, the motors won't work if "PID Control" is checked and you don't have an encoder. ("PID Control" tells RobotC to regulate the motor speed using the encoder.)