Hmmm.... I would have thought the glow plug as well.
Have you tried the glow plugs in another engine?
Are all of the glow plugs new or were they all used?
Does the car run with the glow plug starter attached? Don't go very far or very fast, as it will fly right off and you can dent it.
And just to throw it out there, what number glow plug and what % nitro are you using?