HTML 5 Appcache works in safari/opera/chrome but not firefox

Question

I have an html5 appcache running on a website, it works fine in Safari, Opera and Chrome but it fails to work on Firefox.

I have the following in my code:

Answer 1

Earl's answer above worked for me in combination with turning FireBug off.

In Firefox Preferences -> Advanced -> Network, in the "The following websites have stored data for offline use:" list, do you see your website? If so, try clearing your website from the list and then reloading your website.