Unfortunately this is something that should be addressed in the next version. They have not added a "Browse" button so that you can manually locate your browser.

What you need to do is type in the path to your netscape script, located in your netscape folder, or whever it is installed.

Forinstance for me...

"/usr/local/netscape/netscape"

I'm also running netscape 7. This should fix your problem, but if it doesn't let me know.