Permission Denied

are you using a framed window?
more exactly: are you using files from 2 domains?

I would suggest you to open the editor in a popup window, so the problem goes away (due to security restrictions any browser doesn't allow to read the location of another frame if it is placed in another domain)

Or you could of course work with the source and find the place where the check for the url params is done. Doing a quick search I think that this line might be part of the problem (in fckeditor.js):

var sFile = (/fcksource=true/i).test( window.top.location.search ) ? 'fckeditor.original.html' : 'fckeditor.html' ;

maybe putting it as
var sFile = 'fckeditor.html' ;
fixes your problem,
You'll need also to disable FCKConfig.AllowQueryStringDebug
if that works for you then it would be a matter of putting a try statement around it and submitting it to the patch tracker so Frederico can add it to the next version.

Thank you bleutuna! I was getting the same error instantiating FCKEditor in a frame within a different domain. Putting "var sFile = ..." into a try/catch statement did the trick!

Thank you alfonsoml for your suggestion ! I have the same situation as bleutuna.

For me, I also need to modify the function GetUrlParam in the file editor/filemanager/browser/default/browser.html to solve the problem.

Indeed, the window.top.location.search was also called here...
I didn't know how to replace it so for testing, I only put :

function GetUrlParam( paramName ){
return '' ;
}

Like this, it seems to be working but maybe something else will be wrong now ?? What do you think ?

Do not change editor/filemanager/browser/default/browser.html and don't make it return '' it just creates an XML-error when opening brower.html.

It is no problem that browser.html looks for top.location since it opens in a new window.

Just change
var sFile = 'fckeditor.html' ;
and
FCKConfig.AllowQueryStringDebug = false

That works great for me