Whilst running my car (HPI rs4 3 evo) this afternoon the engine just seemed to jam up and now wont start[]

The car was running fine, i brang it in to refuel it and straight away took it out to start playing with. I have the roto start car and upon priming the engine and placing the glow plug in the car and then using the roto start the engine seemed to jam. The roto start would not turn over the enine and neither could i turn the fly wheel. I have taken out the glow plug but still the engine would still not turn over, it feels asthough it is jammed, what could it be and how can i sort it?

Any help, or suggestion would be GREATLY appreciated.