Does the same thing happen in safe mode? Hold Shift when you launch TB.

Address books in TB are defined for the profile, which can contain many accounts, so deleting an account does not affect the address books, unless the address book is stored in a network location that depends on the account. But not if it's just a standard, local book.

Safe mode also freezes. Because the University of Notre Dame will no longer download to TB, my ND mail is forwarded to Yahoo/sbcglobal which will download to TB because I have a security key with them. I deleted the ND account from TB on 11/6 because of the little window that kept saying I needed to put in my password. Several days later, the ninth or the tenth, I began to have this problem. Deleting that account may have nothing to do with the problem. It's quite mysterious.

UND's mail system is provided by Gmail, and Gmail changed its OAuth authentication about 2 weeks ago, causing mail clients like TB to fail to connect to gmail accounts. This is fixed in TB 60.9.1 and 68.2.1. Is your address book synced with the contacts of a UND account? The gContactSync add-on hasn't been updated yet to address the fix.

While I was traveling in October I received a message from UND that starting October 31 they would not download to TB (security). Because TB mailboxes contain decades of meetings, etc. for me, I wanted to still use it so I came up with the forwarding system. OIT at ND actually directed me. ( You write that this is fixed in TB 60.9.1 and 68.2.1? So TB could still be used with UND? I'm old and confused. They lied?) The address book for ND appears to be synced to ND. I appreciate your thoughtfulness and knowledge. With some idea of the whole picture for me, what would you advise? My current slipping among TB, ND's gmail, sbcglobal is rather baroque. Thanks so much, an octogenarian retiree.

Google and many service providers try to discourage the use of 3rd-party mail clients like TB, using the excuse of 'security', 'less-secure apps', 'two-step verification' etc. They prefer that everyone access their accounts through webmail, either for tracking/advertising purposes, or to avoid having to answer questions from users about the many mail apps. If your TB address book is connected to a non-working mail account, then you could simply move the contacts of the synced address book to a new one that isn't synced, and continue to use it with other accounts. Create a new address book from File/New in Address Book, and move contacts by drag and drop.

But I admit I really don't have a clear picture of how your accounts are set up.

You are most patient. My address book was set up before the beginning of time as "all address books" and under that "personal", then Notre Dame, and then collected. Personal and collected are evidently in my computer. Notre Dame is connected (I checked properties) through SSL or something like that and its host, etc.

I do not need the ND book since I have most of the addresses I need or can find them in departments, etc. It only fills my screen with 500 students named Kelly or Kim. However, when I tried switching to just personal or just collected, the same freeze happened. Then the program had to close and when it was reopened it was on all address books again. I tried writing from address book, same issue. I don't know how to think any further. Sorry.

Your original problem was having address autocomplete freeze when composing mail. The autocomplete process scans all address books for matches, hence the freeze when it searches the ND book. Either delete the ND address book or disable the sync operation.

Thanks for exemplary patience. It seemed to me that it had to be something with the ND address book but I've gotten myself out of my depth too many times by charging ahead. You've explained the logic of the whole matter very clearly. I just deleted the address book since I have no idea what it means to disable the sync operation. It doesn't matter now.