I have to say (with some shame) that I ended up taking the truck to the local Toyota dealers and let them deal with it. I tried pretty well everything I could (except the birthday candle trick - I didn't get to that, but thanks). The dealer ended up having to remove the calipers and then drilling the old pins out. They also fitted new discs, so now I am $600 lighter! Apparently the reason is the pre-treatment salt (potassium chloride) they have started using here to battle the winter snows. It is considerably more aggressive than the old sodium chloride.
My next job now, of course, is to get to the rear drum brakes. Hopefully they are not too rusted up. However, I understand you can force these off by screwing a couple of bolts into holes pre-tapped in the drums. Anyone know what size (and thread) these holes are so I can just go buy the bolts and have them at hand when I start? (I have a 2002 V-8 four door Tundra)
Again, Thanks guy's for all the advice. My advice? Hose the darn salt off after every winter trip (always assuming the water isn't frozen in the hose pipe!)
Giles..