After the upgrade to 60.3.2 on the *second* time it was started Thunderbird started vertically maximized, had forgotten the currently selected folder, was displaying the messages pane under the list of mail headers, and had lost the calendar button & tab. IE, the UI state was "forgotten". Everything else seems to work fine, including Lightning (after the UI tab is shown). Attempted remedies so far have been to remove all cache entries and all .msf files (which have subsequently been regenerated). The installation is as follows: [Win7 running in VMware Workstation] This is an ancient installation that has been running Thunderbird for next to forever (IE, since XP) and has been upgraded many times. The Profiles directory and all the mail account folders have been on a Windows Share for at least 6 years and have not been moved or abused or accessed from anywhere except one VM. The Windows share is done over the network with standard windows security. The share is located on a hard drive on the computer hosting the VM. It does not use the VMware shared directory setting/option. profile.ini (%APPDATA%/Roaming/Thunderbird) points to Windows Share directory (call it eMail_Win7/Thunderbird/Profiles), with two mail accounts located in directories that are siblings to the 'Profiles' directory on the share. The user running Thunderbird has full control (file access) over the directories and all parent directories. Symptoms: * As long as as Thunderbird is running there is a .startup-incomplete file in the Profiles directory. * When Thunderbird starts the {xulstore,addons,extensions,...}.json files disappear and are effectively "replaced" by like named files with a ".tmp" extension. * When Thunderbird terminates, the *.tmp files are left. * The parent.lock file always seems to be present whether Thunderbird is running or not... task manager all processes does not show any other processes. I have a couple of backups of the eMail_Win7/Thunderbird directory and found that if the *.tmp files are removed prior to restarting Thunderbird and replaced with the backed up versions everything runs fine... until the end when the original files have been removed and the *.tmp files are again left. Also, manually renaming the *.tmp files back to the names they should have effectively "fixes" the UI problem on startup... as expected. I normally run AVG virus and have done a full scan of the VM. I have also run MalwareByes and another malware scan (ADW?) and found nothing. In the process of attempting to 'fix' this I ended up dropping back to a system restore point, removing 60.3.2 and reinstalling 60.2.3... to find that Lightning really didn't like that - so 60.2.3 was removed and 60.3.2 was re-installed... which means that files may be in an inconsistent (read 'screwed up') state. The developer error console ends up looking like the attached image (several displayed 'file in use' errors). ... so it *appears* that some Thunderbird task is interfering with some other Thunderbird task in 60.3.2 as there is nothing else using these directories or files. I *can* restore the entire VM and external shares to the state they had on 11/18/2018 (before the update was applied), but I don't want to be forced into that unless I have some confidence that the subsequent update won't go exactly the same way as the last one did... IE, at least identify (if not fix) the current problem or what went wrong in the update. I'd appreciate any suggestions as to what to try or where to go next with this... Thanks, Gary