Is this Thunderbird safe mode, not a safe mode for the Mac operating system? If it's the first, then safe mode has disabled all your Thunderbird themes and add-ons. Since Thunderbird works fine without them, but not with them, you have to work out which of them is causing it to misbehave. It's a trial-and-error process: re-enable them one at a time and test Thunderbird as you go, until you find the culprit. There may be an updated version of that one that you could install, but there's no guarantee.

Thanks for the suggestion - Yes it is TB safe mode. I permanently disabled all add-ons, toolbars and controls but the problem persists when I open TB in regular mode

Are you using:

1. Thunderbird default theme or one you have downloaded?
2. Hardware acceleration ?

Try: If using a downloaded theme: Select 'Thunderbird default theme

If using hardware acceleration: switching off hardware acceleration: Thunderbird > Preferences > Advanced > General tab uncheck 'Use hardware acceleration when available' click on OK

Restart thunderbird.

Not using hardware accelaration.

Don't recall installing a different theme BUT I can't even find where to check or change the theme in TB

does no one have any further suggestions?

since updating to TB 45.0 TB only works in safe mode - when I reopen in regular mode messages do not load or else take minutes to do so.

I have disabled all add-ons; am using default theme

Move the tb config folder to something like ~/Library/Users/<username>/TB-backup and retry launching in 'regular' mode

Which addons are installed per Help | Troubleshooting?

(both enabled AND disabled)

Is this the info you want?

Crash Reports

 Extensions
   Lightning, 4.7, false, {e2fda1a4-762b-4020-b5ad-a41df1933103}
   Quicktext, 0.9.11.6, false, {8845E3B3-E8FB-40E2-95E9-EC40294818C4}
   Signature Switch, 1.6.14, false, {2ab1b709-ba03-4361-abf9-c50b964ff75d}
   Theme Font & Size Changer, 45.4, false, {f69e22c7-bc50-414a-9269-0f5c344cd94c}

DO YOU Think I should try removing (rather than merely disabling) the add-ons?

I should add, though I guess it is obvious, that all of the listed extensions are disabled in safe mode and presumably in regular mode as well (I permanently disabled them)

bherlich said

DO YOU Think I should try removing (rather than merely disabling) the add-ons?

Yes, please try removing one at a time. (ordinarily you shouldn't need to - be something strange could be happening)

I have now removed all add-ons (one at a time) and still have the same issue. Do we move on to the plug ins (all are currently disabled and set to never activate) they are: Adobe Acrobat Default Browser Helper Dymo label plug-in Java Applet plug-in SharePoint Browser plug-in Shockwave flash

Plugins should have no effect.

Safe mode affects more than addons.

   The Just-in-time (JIT) JavaScript compiler is disabled. 
   The userChrome.css and userContent.css files are ignored. 
   The default toolbar layout is used. 
   Hardware acceleration is disabled. [HWA]

Easy to check HWA. In normal startup mode visit edit > prefs > advanced > general. Is HWA checked ON?

no HWA is NOT checked (by the way, if it matters I'm running on a Mac)

If all your accounts are imap, please try creating a new profile. (don't delete the old one) See https://support.mozilla.org/en-US/kb/using-multiple-profiles

well I think I blew this one - it allowed me to create new profile (but I chose POP and I dont think my other accounts are IMAP) and it is now in the process of downloading 18, 000 emails, with no file structure to my inbox

(A pop account with 18k messages in the Inbox is not good.)

So the original problem is gone when using the new profile