Thanks I didn't know that, what about all those vintage pickups you see, are they rebuilt?
Forgot to mention earlier that it's slightly possible to damage a Strat pickup (a Strat pickup with staggered-height poles) if you decide to reduce the height of a AlNiCo pole by filing too aggressively. You can reach the melting temperature instantaneously by filing aggressively. AlNiCo material starts to lose its magnetism as it approaches and exceeds its melting point.
Actually, the aggressive use of a file mentioned above is a bit overblown. If you find yourself needing to reduce the height of a pole in Strat pickup, all you need to do is perform one stroke at a time with the file and you should easily be safe from damaging the pole magnet. Whatever you do, just don't use a bench grinder.
PS: The most likely cause of the original poster's problem is a bad pickup selector switch.