honestly, that has me completely baffled. The only possible thing it could be would be your swing arm binding. Which actually makes sense. Because it would bind like that if the axle nut was tightened down too much. Which would also make it extremely difficult to remove the nut.
The only other thing I can think is that your chain is binding somewhere. Check the tension while you're working back there. You should have about an inch and a quarter - an inch and a half of play half way between the front and rear sprockets (bottom of the chain).
Link to original page on YouTube.