From your original description of the fault I would say (as per other posts) that the battery has 'died' - As to why, this will need further checks. If the engine had 'siezed' then the back wheel would have locked whilst riding it (or, at the very least' a rapid de-acceleration accompanied by load mechanical noise). 1. Check battery voltage - If low, disconnect and re-charge. 2. Ensure bike is in neutral, remove spark plug and connect to HT lead, keeping the body of the plug touching metal. 3. Turn on ignition and try starter (checking spark). 4. Turn on lights and try starter - If lights dim, then battery or starter is 'dead'. 5. If all good - re-fit plug and try to start. If bike now runs, check voltage at the battery (should be around 14v), switch on lights and re-check (should be around 12.5v). I would suspect this is where you will identify the fault. Good luck!