Over the years, Jehovah's Witnesses have been accused of not being Christian, because of the unusual understanding they have about the nature of Jesus, and their denial that he was God incarnate. In order to counteract this critisizm and reinforce the conception that they are Christian, mostly to their own members, they began inserting the label "Jehovah's Christian Witnesses" in their literature. For a while, it became a very popular euphamism in their own minds.
Unfortunately, morons that they are, they forgot to actually register the name. Meanwhile, another group did register it. So, the Society had to stop using it.
A search on "Jehovah's Christian Witnesses" will yield a few defunct links to outreach ministries, so I think the new group withered.
At least, that's how I heard it. Can anyone verify or add to this?