How do I link to an internal site page (joomla site)?

I administer a Joomla 1.0 site. I have just installed FCKEditor and am getting familiar with it. I am trying to create a hypertext link to an internal page. I am trying to use the Browser Server button on the Link Info tab of the Link dialogue box. When I click on the Browser Server button I get a window that pops up with a 500 server error "Server didn't send back a proper XML response." Can anyone tell me what I need to do to easily create a link to an internal page? I need to make this as easy as possible for my client who will not have access to the backend Administration to obtain Joomla-created URLS (I use OpenSEF).

thank you!

By the way, I did check the fckconfig.js file and FileBrowserLanguage is set to 'php' for my Joomla site. Is there something else I need to check or is this just some security issue?

I also ran the connector test and received: The server encountered an internal error or misconfiguration and was unable to complete your request. Please contact the server administrator, .....

I also see this advice in the FCKEditor documentation, but I don't understand it (which file to check). Can someone advise please:

Another thing to check is that the target folder for the files exists in your server. By default it uses the "/UserFiles/" folder, but it is configurable.

The editor uses a fixed structure in the target folder that separate files used on different dialog boxes, respectively the link, file and flash dialogs. For example, if you are using the "/UserFiles/" as your target file, it will use "/UserFiles/File/", "/UserFiles/Image/", "/UserFiles/Flash/" and "/UserFiles/Media/". The connector tries to create those directories automatically, but on some configurations they need to be created manually to make it work properly.