Sorry, I don't have an answer to your question, but I do have my 2 bits to throw at you.
That would also annoy me to no end if the train can't run on the included track. But having said that, I'd triple check the derailing truck to make sure it's not binding and has complete freedom of movement. If it has an electrocoupler, I'd make sure the wires aren't catching something and keeping the truck from moving. Also, did you try running the locomotive the other direction around the track?
