Using version 52.91 32bit I have 3 profiles, one of which is just the calendar. The calendar access 6 calendars eg google calendars (my family's calendars) When I opened the calendar profile the calendar was not there. Lightning add-on was no longer installed. Installing addon and full restart fixed problem. But problem keeps reoccurring. Operating on Windows 7 32 bit Another problem which may be related. After hibernating Calendar get script errors. To avoid this I close Calendar profile before hibernating. Grateful for any help