Certainly could be Bernie, the cheaper air cooled "buzz boxes" don't have a massively high duty cycle, although I would have thought you would get more that six rods out of it! If it's running that hot I would have thought that the thermal cut out would have stepped in before the plug melted! Having looked at the pics though, you appear to have a continental type plug which goes into an adapter. Each connection you have will have some impedance and this will generate heat. I imagine the adapter was the weakest point, hence the burn out. I would cut the plug off and replace with a good quality heavy duty 3 pin plug and you should be ok. The heavy duty plugs are a bit more substantial and can handle the current and the heat build up better.