Some of the Dog Whisperer's advice might be helpful. I have watched quite a few of his shows and it is amazing how quickly he can change dog behaviors simply by understanding what to do. I'm not an expert, but I can pretty much guarantee that the verbal "shaming" after he chases a cat is not going to work -- it will always come too late after the fact, so that the dog will not make the connection between the cat and the shaming. Basically he will feel punished but not understand what it's for. Any correction has to be done in a specific way and immediately (preferably before the behavior even occurs). My guess would be that you need to encourage "bonding" between the dog and the specific cats. There are techniques for doing this (I think clickers work for this kind of training -- on both the cats and the dog!). Actually, your best bet might be to consult a good dog psychologist for advice.