short-circuit,
Are these bulbs used in an inverted position (upside-down) by any chance?
I read somewhere some time back that that sort of thing is to be avoided,as it is easier for the broken portion of the filament to bridge the filament stanchions.
As Greg mentioned, there isn't really an easy fix as long as you want to go fusing your switch wires (feeding the lamp circuits.
The only other thing I could suggest is (not sure if they exist in the US) rough service lamps, where the filament has more filament supports than a standard bulb.
