Comment 8 for bug 1072864

Just some ideas:

Go into calendar tab of TB and right-click on calendars and choose properties and check that refreshes occur less frequently, mine are all 30 minutes.

Lightning 2.6 has patches which can be applied to handle google's changes to authentication. In fact, my understanding is any older version of lightning will not work with google calendars. And, I believe TB 24 is needed too.

For email address problems, also check calendar properties, and check that the email address of the calendar is what you intend.

I've noticed in my TB that whatever calendar I last selected in the calendar tab before closing is now the default calendar.