This could very well be the solution if you have one plugged in. I had a problem with a demo posted here not too long ago where the vehicle wouldnt stop going backwards... Come to find out my controller was plugged in and was causing the vehicle to go in reverse.

http://www.freewebs.com/otama_syndicate/index.htm - Each master to his own technique.

- Not me said the bee, Nor I said the fly.