Some electric models require you to calibrated the ESC. There is info on our help page at http://www.nitrotek.co.uk/help.html
Also the first time you push forward on some controllers it will only put the brake on and then the second time will be reverse. This is done so that if you are racing and you need to slow down for a corner the model does not go into reverse and break.
Finally make sure that you do not have your throttle reverse switch on, ie. when you pull the trigger the car should go forward and when you push it forward the car should go backwards.