Cannot add my domain

[therealanna]

I used the "Addon domains" section in cpanel and tried to add my domain. Here is the error i got:

So I tried to remove the subdomain therealanna.x10hosting.com and this was the other error I got:

when I go back to add on domains there are no therealanna.com

So weird.. I've used Cpanel before many times, this is a first.