2000 t300 joystick control dies when going forward

[Jray12]

I have a 2000 model t300 with the joystick controls that has an intemittent problem. Sometimes when operating the forward controls it will just shut the engin down, i have to shut the system all the way down re-enter the security code to restart it. Sometimes it will be fine for a while and sometimes it will just shut down over and over again. Any ideas as to what the problem might be? Any help is greatly appreciated. -Jesse-