Review for Provider for Google Calendar by ohmjohn
Rated 4 out of 5 stars
I may have a solution for the problems described in 1.0.2. I had the same troubles. I found out that clearing the password manager in Thunderbird (for the google calender items; not for imap etc) did the trick.
After that reinstall your calender and it worked for me. (till now)
To create your own collections, you must have a Mozilla Add-ons account.