Just when I have almost given up on the broken Adsense Notifier script, it got updated and fixed! You can download the latest version here: Adsense Notifier.
The current version is 0.9.6, and it once again shows all the Adsense earnings in the toolbar of my Firefox.
Adsense Notifier is one of the most useful extensions for me, because it saves me the effort of regularly checking the status of my Adsense account (which is a very bad habit – wastes a lot of time). Simply configure the settings to your likings, and all your vital Adsense stats will be automatically downloaded and delivered to your statusbar. Incredibly useful!