I'm note sure what to do here... unfortunately, I'm a complete novice with the UV editor in Carrara (I've been doing all my UV mapping in Wings, too).

One thing to try at this point would be to delete the floor from the scene, insert a plane, then map your texture on it. The plane is already oriented correctly when it imports. If you need to keep what you have, it looks like the UV map will need to be re-done, I'm afraid.