Why does the ferret bite the dog?

We have two ferrets and one Jack Russel Terrier. The Jack Russel is aggressive towards all animals so we always made sure to keep the ferrets and her seperate. One of our ferrets died about a year ago, of natural causes, and so just a few months ago we got another new ferret from the resque. This means that the ferret is not a baby, she is probably about three. The ferrets seem to get along just fine, except the new one bites, but the old one does not seem to mind, she just plays. But the problem comes in because the new ferret is very mischievious and gets into everything. One day the ferret climbed up golf clubs (we still are not sure how that happened) and got in the room with the dog. Surprisingly they both did fine, so we decided, under close supervision for the first few times, the dog and the ferrets could be in the same room. The dog played with the old ferret, and all was great, then when the dog went to play with the new ferret the ferret ‘played’ back and bit the dog, clamped on her tail and would not let go. Then did the same to the dogs nipples a little later, now the dog is terrified of the ferrets (probably because the two ferrets look identical so she cant tell which is which), and the new ferret is continuing to bite the other ferret. Is there something we could do to make her stop biting? and is there something we could do to help the dog no longer be afraid of the ferrets??