he is talking about a stuck COG. Reverse rotafix didn't do anything???
I freed up a stuck cog once by standing on the padals (lockring removed) and jamming down on the pedal REALLY HARD. Had a friend hold the bike balanced for me. Just stomp on that ****. Backwards, of course.
I really don't know if this method is advisable (for those with more experience) but it did work. There could be a chance of stripping the hub, I imagine.
I have also heard of people using wood blocks and a large bench vice. Cog teeth stuck into wood blocks, clamp into vice and turn wheel. Make sure you turn the wheel in the right direction (lefty loosey, but when upside down in a vice turn opposite direction).