rc-fiend, i too have had problems with those little glow drivers, and eventually threw the lot out, and invested in a power panel for the flight box, operated by a gelcell 12 volt battery. Since then i have never had a problem, as the power panel has an outlet for the glow driver with a meter and variable control on the heat. I just checked my logs and the power panel has started my aircraft 8326 times, no problems at all. So it will be a help to invest in one to fit your flight box.
Bill:- down-under in Australia