Error message when submitting site name to

Hi I have gone to make a 2nd app for the other site in my multisite mapped domain wordpress installation and when I have entered in the app domain box, it has come up with this error message again and yet I have only entered the one domain.

This must be derived from Canvas URL, Secure Canvas URL, Unity Binary URL, Site URL, Mobile Site URL, Page Tab URL or Secure Page Tab URL. Check and correct the following domains: