A guy posted here about an engine that the piston was siezed in the cylinder on and he recommended antifreeze over night or (if you can avoid the fumes) heated. I've never tried it. I would probably apply a moderate amount of propane torch heat to it. If it's stuck from baked on castor oil some guys will advise you to soak it in fuel overnight. Personally, I would soak it in lacquer thinner overnight and resort to a propane torch as a last resort.
What ever you do don't pry on the ring because you might break the it or gouge the ring groove (ring land) in the piston. If you are going to replace the ring a broken ring makes a good cleaning tool for cleaning out the ring groove. Careful here. If you are going to use the ring as a cleaning tool be sure to file the end of the ring smooth and slightly radius the inside corners of the ring that rests in the ring groove toward the piston so that you don't gouge the piston groove. Does that make sense?[sm=confused.gif]

Good luck.

Bill