Generally, the only thing that stops plugs firing is a short between the centre and outer electrodes. The internals are a pretty solid unit, so I suspect as Wayne says, there's something going on with the mixture.

Have you tried cleaning the plugs with something like brake cleaner and using them again?

Not sure what could be wrong on the ignition side to knacker them, they've been desinged to run at thousands of volts and the NSR is unlikely to be producing more without having serious consequences with other parts (ie if it was putting out 20 volts, then I suspect the coils would produce more output, but the rest of the electrics would fry...)
_________________
MC21SP Plaything
BMW F800GS Bumblebee
Triumph 9551 Daytona Big boys toy
FJ1100 Sporting relic
GTS1000 oddball