It's the bulb itself. I've had one burning in my other Silver King Nut Machine for about 6 months now with no problems. Sounds like you might have a bulb with too low a wattage rating. The flasher bulbs work by heating up just enough to begin opening and closing a disc contact and that gives you the intermittent action. If you pump to much juice through it, it won't work correctly and the contact will stay closed because it can't contract into the open position.
There is also a product called a flasher outlet that can be plugged into any 115VAC wall outlet. You then plug into it any light fixture (except flourescent!) and it will flash.
http://electrical.hardwarestore.com/12-34-outlet-adapters/outlet-flasher-235325.aspxI can send you a bulb, PM me with details!
