Using fckeditor 2.6.4.1 on different sub-domains

I have a domain on which I have several sub-domains and I'd like to use fckeditor 2.6.4.1 on the sub-domains. I put it on one and it works fine, but I can't get it to work on the other sub-domains.

I've installed the program on the other sub-domains just as I did on the first, but I either get a message saying the website is not there (where the editor should appear), or I get the actual website of the first domain I installed fckeditor on (where the editor should appear).

I'm using the php version.

On the page where I am wanting to use the editor I have this at the top of the page:

include($_SERVER['DOCUMENT_ROOT']."/fckeditor/fckeditor.php");