Have you made sure that you've replaced the previous file and not copied it?
Make sure that you have, and make sure the texture is named ftailMask1 if it is the tail's mask you are having trouble with. Or make sure that the fur texture of the tail is called ftailShade in order for things to work as it should do.
Retrace your steps and you'll find out the problem.
If you're still having trouble, come back :)