mine would occasionally slip into reverse because if i remember correctly there is a little metal "pathway" - for lack of better term that it it supposed to go into. when it gets worn, it can easily slip into it reverse while you are trying to start out in first. take the knob apart and start fiddling around below the boot and you'll see what im talking about.

try starting in 2nd gear, will that get it going forward, or does it stay in reverse when you have it in 2nd?

470K! makes mine feel young at 225!