• Please start *Windows* in safe mode with networking enabled - https://support.microsoft.com/en-us/help/17419/windows-7-advanced-startup-options-safe-mode#start-computer-safe-mode=windows-7

• Still in Windows safe mode, start Thunderbird in Troubleshoot mode https://support.mozilla.org/en-US/kb/troubleshoot-mode-thunderbird

Does problem go away?

- If no, then cause is either: bug in Thunderbird, something (eg a setting, file or folder) in your Thunderbird profile, your mail provider. Please post into topic the contents of Help | Troubleshooting | copy text to clipboard

- If yes, the problem is gone, then (still in Windows safe mode) ... start Thunderbird normally -- If problem is still gone, then cause is likely a program loaded during windows startup. Possibilities include: antivirus software (AV), virus/malware, background downloads such as Windows or other program updates, to name a few. For AV information see https://wiki.mozilla.org/Thunderbird:Testing:Antivirus_Related_Performance_Issues -- If problem came back, then cause is likely a Thunderbird add-on - eliminate them by disabling add-ons one at a time in Tools | add-ons | extensions and restart Thunderbird after disabling (if you have many add-ons, try disabling half of them at a time)

- If results are unclear ... possibilities include temporary conditions such as contention from other running programs, downloads related to windows update, ...

Please let us know your findings.

Thanks, Wayne!

Tried same routine on DW's computer (same hardware, software, two TB profiles). TB was working. Updated to 102.15.0 and restarted one profile (Gmail). TB was working. Seems to rule out bug in TB, trouble with Gmail.

Had not done a normal reboot before posting question (mybad--jumped the gun), so I puzzled whether to follow your instructions or do a regular reboot first. Decided to try regular reboot: One profile tried, opened okay.

I then backtracked to your instructions. Opened in Safe/networking. Opened (one profile of) TB in troubleshoot. Opened okay.

Closed TB and launched four profiles (of the five I normally have open). All opened okay.

Rebooted into regular Windows. Opened all the other apps I normally have open, then relaunched TB. All five profiles opened okay, are working fine.

The only thing I noticed is that on that first regular reboot, my anti-virus updated itself. I guess we'll never know if that was the problem or part of it.

I'm guessing I just need to reboot Windows more often, clean out junk in memory.

Thanks for your help!