The latest update, 52.1.1, seems to have some problem recognizing the existing profile file. I had the same problem and the profile is still on my computer in the proper location, but for some reason Thunderbird is not recognizing the location. Running the Troubleshooting help shows the profile file and all the mail and other files, but the program is just not recognizing it. I don't have a solution, though I'm still trying to find one. There doesn't seem to be anyway to contract Thunderbird directly, but I did post on their Facebook page.

http://kb.mozillazine.org/Recovering_a_profile_that_suddenly_disappeared

Do you use the program CCleaner? What antivirus are you using? What version of Thunderbird do you have?

Thanks Airmail. My problem turned out to be the perfs.js file - all the "mail.account" entries were missing. I had a good copy of the js file on a backup and replaced the corrupted file. Everything seems to be OK now. Thanks again.

jhburgess said

Thanks Airmail. My problem turned out to be the perfs.js file - all the "mail.account" entries were missing. I had a good copy of the js file on a backup and replaced the corrupted file. Everything seems to be OK now. Thanks again.

Do you use CCleaner? It is known to do what it thinks is best for that file and it never ends well.

Airmail, yes I have been using CCleaner, currently version 5.31.6104 Pro. Perhaps that's the problem as the prefs.js file lost the "mail.account" entries again when I closed it. I've restored the original js file and will discontinue CCleaner to see if that ends the problem. Thanks for your help.

Thank you for the reply I have been using CCleaner 5.31.6104 so that may be the cause but I am not too sure what steps to take now to solve the problem. How do I restore the original js file please? Any help that can be given would be very gratefully received.

jimirving, First, update CCleaner to version 5.31.6105. That may keep it from changing the prefs.js file in the future. To be safe, in CCleaner in the Options section, select Exclude from the menu on the left side of the screen. Then click on the Add button for files or folders to be excluded. You can then select your Thunderbird profile folder to be excluded from CCleaner or the specific prefs.js file in your profile. I excluded the js file on mine and so far the problem has not happened again. As for restoring the corrupt prefs.js file, I was fortunate to have a good copy from an earlier backup which I used to replace the corrupt file. If you don't have a good copy you can use, you will need to follow the procedure for "Corrupt or empty js file" in the link above posted by Airmail.

Many thanks. I did have a good back up and using your guidance the problem has been solved.

It is strongly advised that you do not have CCleaner or any other similar product scanning any Thunderbird folders.

CCLeaner is well known for deleting files which it should not be anywhere near and causing much inconvenience to the user. Thunderbird has files that keep session data, preferences, passwords, email addresses etc etc and CCleaner is doing what it was instructed to do, clean up files, delete passwords etc etc. If you wish to use CCleaner because it can be useful, please set an exclusion for Thunderbird folders.

Glad to hear it worked out Jim. The credit really goes to Airmail as I basically repeated his advice to me. I spent the better part of a day getting very frustrated before Airmail saved me. As you probably know, Thunderbird also did an update to 52.2, so maybe that will help in the future as well. Still not entirely sure if Thunderbird's update to 52.1 confused CCleaner and caused it to treat the prefs.js file as corrupt, or if the CCleaner update erroneously treated the file as corrupt. I'm sticking with the exclusion in CCleaner just to be safe.

Thank you again for the advice I will err on the side of caution as you suggest