This problem exists on both my application and the Demo site with Netscape 8.0.

When you click on the downloadable files icon the dialog boxes opens up but fills the entire page. When a file is selected and the Insert button is clicked nothing happens. The link is not inserted and the window doesn't close. In fact, I'm not sure a popup window actually was opened. The only way to exit the dialog is to cancel.

 

This problem does not occur with FireFox. It works fine there.