jkoral's method (above) saved me when the rubber mallet & kicking the rim failed to do loosen one of the wheels. After cleaning up the hub surface I applied nickel anti-seize. I don't know if this is better or worse than copper or zinc based anti seize in this application, given the potential for electrolysis(?)
In any case, that was 4 months ago. I've had the rims off a couple of times since with no fuss
