I use Mozilla Thunderbird 12.0.1 in Windows 7 and my calendar (agenda, events, tasks, etc.) disappeared since last update. I've read other users' questions/answers and some tips concerning the calendar but didn't find a solution to my problem. Calendar Tweaks 6.3 is on my add-on list but I have no access to it. In fact, I don't even know if this is where my data was saved. I'm far from being a computer pro and would appreciate any suggestion. Thanks in advance.