How much memory is Thunderbird using when this issue is experienced? Try restarting Tbird in safe mode, note how it behaves. Also, create a new profile, cancel the existing account wizard, close Tbird, copy the address books to the new profile folder (replacing the existing empty ones) and start Tbird using the new profile. See if the same errors arise and if the address books are loaded without a fuss.

Thanks Stans

Forgot to mention in my description: - tried several variations in safe mode, with no difference in the outcome - using Bitdefender, so not sure if it is causing the problem (will try to run TBird with Bitdefender turned off, but I will have to do this later).

Memory is only about 173 Mb for explicit allocation, with 4 Gb allocated to address-space, but 75% of that free. There are many other entries, but I am unsure which you would want.

If I open Address Books first and then TBird, explicit allocations is 267 Mb, and address-space has virtually the same 4 Gb.

I managed to save the profile to another location and created a new one. I copied all of the address books from the old to new profile. Opening TBird again is no problem, and the collected and personal address books are there with all of their addresses. Of course, the other address books were not recognized, as I had not created them in TBird.

I then shut and open TBird again, created 13 address books (A1 to A13), shut TBird and opened it again to make sure the address books were there (which they were). I closed TBird, deleted 13 of the address book files in my profile folder and replaced them with the copies of the 13 address books in my original profile.

When I opened TBird, there was no warning message and the address books were all there. Yeah! The address books themselves seem not to be the problem.

In that process, I noted in my original profile that I have two impab.mab (impab.mab and impab3.mab) files, which I understand are hangovers from importing addresses donkey years ago. However, I also have four versions of .bak files for the impab3.mab file (impab3.mab.bak, impab3-1.mab.bak, impab3-2.mab.bak and impab3-3.mab.bak), all created within a couple of hours when I was trying to resolve this problem, and all with no content. Not sure if it relevant, as I tried moving the impab files and .bak versions out of the profile and it made no difference.

Couple of other trials: - renamed global-message-db to rebuild it - no difference (did not expect it to, but tried it).

- deleted session-json - no difference

- saved the pref-js file with an old name and opened TBird. It lost all of its related content (TBird wanted to set up a new profile , etc.), so there was no error message about the address books because it did not recognise the address books.

- opened the original pref-js file in Notepad, and Address Book 6 is the first address book called (first listed).

I have also tried several other options, with no real success: - I saved new entries to Address Book 6 - no difference. - In TBird, I created a new address book (14), then closed and opened TBird and got the error message saying Address Book 14 was the problem (a check of pref-js file shows that Address Book 14 was then the first in the section of Address Books, with Address Book 6 next). - In TBird, I moved the contents from 6 into 14, then closed TBird and renamed 6 in the profile folder, which meant a new 6 was created when I re-opened TBird. In the profile folder, both of these new files were smaller than the original 6, but that made no difference. - in TBird, I moved the contents from 14 into the new 6 and deleted 14 (so in the profile folder, I had a larger old version of 6, a smaller new version of 6, and 14 was gone). When I closed and re-opened TBird, I got the old message about Address Book 6 (which, on checking pref-js, was then listed first).

From all of the above, the address books are probably not corrupted, but when they are opened from within TBird, an error occurs, and the message highlights whichever Address Book is called first in pref-js. Opening Address Books before opening TBird circumvents the error, but I cannot work out where it is occurring.

I have run out of ideas for the moment. Any suggestions?

Apologies, I forgot simply copying any other (user-created address books) mab files except the two default ones does not work. Their contents must be exported and imported instead. To export ALL of your address books (default format is csv format), open the address book of your old profile so that ALL your address books are loaded properly. As per your experimentation, you will have to open this first before launching the full Thunderbird program. In fact, for this export, you don't even need to open the rest of Thunderbird. Select/highlight All Address Books then go to Tools > Export. Select a location (new empty folder is recommended) and click Save for each of the address books. Unfortunately, you have to do so for each address book, but this shouldn't be a problem because the file name and format are automatically filled for you and the save dialog reappears for each address book in turns. In the end, you will have all your address books in a separate csv files. Importing them into the new profile should be straightforward. No editing of the csv files is required before import. You can skip importing the two default address books (Personal and Collected) since those to can simply be copied over using their respective mab files. Also, if you import them, you will have duplicate books (why Thunderbird allows this beats me). You can rename the duplicates accordingly, or move their contents to the default books and then delete the empty dupes afterwards. You will now have all your address books created in that new profile. Test as many times as you can to see if the problem is reproduced in the new profile as well.

Disregard my previous reply since you already recreated the 13 books in the new profile and they loaded just fine. This makes me think something is amiss with your old profile, but I have no idea yet what it could be. It is recommended that you add your profile folder to the antivirus' exclussion list. Bitdefender could very well be tripping.

Thanks again Stans.

I am reluctant to turn off Bitdefender on the whole Profile. What I did do was turn off all of its components before I opened TBird. I got the same message, so it is probably not Bitdefender causing the problem.

I believe you are correct in saying there is something wrong with the old profile. I note that my default.ini and components.ini files were created in 2005, so I have had this set up, transferring it from computer to computer, for many years.

I suspect pref-js, but I do not want to start a new one and have to add all of the attributes. A new file has 90 lines of instructions, while my current one has over 1,500!

I will go away and have another try, but would welcome any further suggestions.

I suspect pref-js, but I do not want to start a new one and have to add all of the attributes. A new file has 90 lines of instructions, while my current one has over 1,500!

You may not have any other choice, besides, most of the preferences will be generated automatically by the program as you set it up to your liking. At this point, I can only think of recreating your profile.

I don't think this is likely to be a memory issue. That said, this kind of report is unusual to be given by a Windows user.