PB with windows dialog

Hello, I have a problem with windows dialog of FCKeditor: when I push button with icon , for example image,the browser is very slow and I obtain this error: "the document doen't contain any data" and a window with javascript code is displayed.

Before I used a SGI (IRIX) serveur and I didn't have this problem. Now I use a FEDORA serveur, and this bugs be obtained with IE and Firefox.

Please help me ,
thanks
dam