My CBC, Phoe, is a plucker.
He came to us when he was 6 months old , barbering his feathers. That quickly turned into full on plucking. He went to the vet, and though his protein levels were a little low, everything else checked out perfectly. We got the protein levels back up by feeding eggs and tofu...but still he plucks. In his case, his feathers come in crooked, which the vet thinks may have been a nutritional problem during hand feeding.
He has a GCC buddy, and they preen each other and cuddle constantly. Still he plucks.
He plays with his multiple toys, eats chop and fresh veggies better than any bird we have, still he plucks.
We chose not to use a collar or sock as I feel in his case it would interfere with his quality of life.
I hope you are able to get yours to stop, and I wish I had the answer.
Here is Phoe, enjoying his chop
I'm not sure if you have seen this thread, but there is a ton of wonderful info here:
http://www.parrotforums.com/behavioral/52217-plucking-search-answers.html