I'm having some weird behavior with my wheelset. When I backpedal slowly, I can see the chain "bind" and hit the chain stay, then push the wheel to rotate backwards. If I backpedal quickly with force, the chain won't bind and the wheel will stay in place as I expect. I'm not riding a fixie!! Is there something up with my cassette body?

I have a chris king rear hub and I'm not sure what's wrong.. Some instructions on how to resolve this would be great. Am I supposed to clean the hub somehow?

If you're not riding a fixie, you really don't have a good excuse for backpedaling do you?

Your chain just doesnt like going through your derailer backwards, thats common enough.

That's almost always dirt and crud that causes that. Clean and lube your chain.

Another possibility is a tight link in the chain. Back pedal slowly and watch as the chain emerges from the rd's lower pulley. A stiff link will show up as a kink in the chain as it comes off the pulley.

Also check the B-screw on your rear der. to make sure the pulley is not hitting the bottom of the cassette cog.

I concur with all the above suggestions, but it could be the freehub as well. I'd take off the wheel and rotate the cassette to see if there's any rough spots or points where it doesn't turn freely. If so, you could try lubing it up (might need to remove cassette). However, its more likely that you may need to get a new freehub.

Also check the alignment of the RD with the cogs. It might need adjustment, or have a bent hanger. And check your cable-tension on the RD as well.

After taking another look at this thread I'm inclined to lean more toward the freehub binding. If it's not turning (backward) freely, then the chain is going to tend to bunch up on the chainstay. Just as the OP states. Just remove the rear wheel and spin the cassette backward, by hand. If it is binding it should be pretty obvious.

So, I'm still in the "clean & lube" frame of mind, but it's more likely that it's the freehub that needs the servicing. I'm pretty sure that if you do a search you can find a service proceedure for CK freehubs.