Recently reminders freeze Thunderbird/Lightening so I must use safe mode to even read my mail, while the calendar (Lightening) is not available.
When I start Thunderbird I get reminders (some out of date) and then both the reminder panel and the Thunderbird panel are frozen. I turned "notifications" off in Google calendar and Thunderbird still hangs. I can read/write my email in "safe mode" but I have lost the calendar functionality. This problem arose recently - perhaps with a Windows7 "update".
Alla svar (2)
If you can read etc emails in Safe Mode then an addon is causing conflict. Obviously Lightning will not work in Safe Mode as it an addon.
Are you using the most up to date version of Lightning?
Lightning 3.3.1
Also: https://support.mozilla.org/en-US/kb/using-lightning-google-calendar
Are you using most up to date version of Provider for google calendar ?
Provider for Google Calendar 1.0.2