Being an ardent Firefox fan, I could not wait to download Firefox 3.5 beta and see how fast it is and what all new features are added. After installing it over 3.0.10 and restarted in anticipation to see something new, something cool, surprisingly I saw a message that my favorite google notebook extension is no more compatible with Firefox 3.5. With utter despair, all thoughts of exploring new Firefox vanished and I started googling on how can I get my notebook back. Didn't had to wait long. Found this quite useful blog which made me happy again with no complaints for Firefox. ;-)
Follow the instruction on above and you can get have your google notebook extension back.
Addition on July 03, 2009 18:41:29
If you are too lazy to do all the above then Steve is your savior. Visit http://www.notebookaddon.tk/ and you can install modified google notebook extension without all the jugglery. Thanks Steve.
P.S.: Above blog also introduced me to a good free archiving utility 7-zip. No annoying winzip evaluation dialogue or winrar's purchase license dialogue. ;-)