Can't see loaded java script from XUL.

Hi all,
I have successfully installed the java script debugger (Venkman).
And if I navigate the browser to an HTML file (that uses java script) and
If I runned the debugger at the same time, I see the script within the
LoadedScripts window correctly (and I can debug it).
However, if I navigate the browser the a .XUL page (that uses java script 
too), the script isn't available in that window.

What is wrong?

Notice, that I see the script through the Open Windows panel, but If I set a 
break-point, the debugger never stops on it.

Thanks for any help!
Honza