toolbar error when using (MAC, firefox)

I have FCK working properly with a custom toolbar, however when a MAC running firefox trys to load the custom toolbar i am presented with a message saying that the toolbar can not be found.

in an attempt to work around the problem i changed the buttons that are loaded with the "Basic" toolbar set to suit my needs, this again worked on PC but when I loaded the page on MAC running firefox the standard "Basic" toolbar is loaded not my custom "Basic" one.

loading the same page running safari on a MAC and it works fine.

the page i am editing to make the toolbar is "fckconfig.js" and i am using the PHP version of FCKeditor.
version
2.6.4.1
Build 23187

any ideas would be greatly appreciated

thanks