Cannot get JavaScript debugger to work. Mac - FF6

I love Appcelerator, but without the JavaScript debugger, its pretty useless trying to do any sort of development.

I am using Mac - Lion FF 6 Atpana Debugger 1.7.1 FireBug 1.8.2

When I launch the debugger, FireFox loads and I see the following message in FireFox: JavaScript Debug Mode: Autogenerated HTML Wrapper (http://i.imgur.com/MKTe5.png)

Titanium Studio loads the debugger view, and everything says its working... I get a list of my breakpoints etc... but nothing else happens. The app never appears to be run and the breakpoints in my script are never reached. The app (a tiny test desktop app which calls a javascript file with 'alert('hello');') works fine when I run it normally, but when I load the debugger nothing happens.

Anyone know how to get it working?

Thanks