At 10:30 EST this morning (Oct 5), my Thunderbird installed an update. Since then, the address book disappeared. I tried importing it from another computer and it says successfully imported, but nothing is there. When I try to send an email -- even replying to one and not manually typing the address -- the email address turns red as if it has an error and it won't send. I recently transferred my profile from one computer to another. For the last few days, everything has worked as it normally would. Today, I thought maybe I'd broken something, so I re-transferred my entire profile from one computer to another. The other computer does not have this morning's update, and everything worked fine. Transferring to the new computer with the update, the address book disappeared again. I'm attaching a screenshot. The email address in red is actually another address of mine and is correct. There's no reason for it to not work. Another screenshot is the empty address book. I've been using Thunderbird for about 15 years now, and have a rather extensive address book that's grown over the years. Please let me know how to make it work.