So, I ran into a bit of an issue when my Lightning on Thunderbird stopped syncing with my Google calendar. I noticed this when I tried creating an event, but did not find it on the calendar. I upgraded to the latest version of Thunderbird (15) and the add-on manager automatically updated the Lightning version. I thought the issue would be resolved. It wasn’t.
Turns out the culprit in my case was the Provider for Google Calendar. The version installed on my machine was 0.13 while the version available was 0.16. Auto updates hadn’t kicked in. When I manually performed the upgrade, I had to recreate the links to the calendars, but everything started working smoothly after.