Restart Thunderbird with add-ons disabled (Thunderbird Safe Mode). On the Help menu, click on "Restart with Add-ons Disabled". If Thunderbird works like normal, there is an Add-on or Theme interfering with normal operations. You will need to re-enable add-ons one at a time until you locate the offender.

Thank you Matt.I had discovered myself how to get into my e-mail account with the add-ons disabled,however I'm not computer literate enough to know how to switch off add-ons individually,so although I can experiment,I may have to wait until my son is here next week-end.

To disable an addon extension you need to open the 'Add-ons Manager' and click on the relevant 'disable ' button, then restart Thunderbird.

'Menu icon' > 'Addons' a new tab opens showing the contents of the 'Addons Manager'

see example image below so you know what the tab looks like

Thank you Toad-Hall for your interest.I have no Add-ons that I have added and when I finally got into the Thunderbird Add-ons Manager there were no Add-ons installed for me to uninstall!The problem has only existed since the last Thunderbird update,so I wonder if the problem is systemic?I can't get any response from Mozilla!

rod.willmott said

I can't get any response from Mozilla!

Probably because the do not do the Thunderbird release or support. That is why we are asking for donations. It can not be done completely by volunteers forever.

No Addon extensions - not even 'Lightning' which may have been installed automatically?

Note: If Thunderbird is not running and you want to start in Safe Mode. Hold down the 'Shift' key while starting the application.

Safe Mode switches off various settings when starting up. One of those is hardware acceleration, so let's start with that. Please see if you have hardware acceleration enabled and switch it off.

• 'Menu icon' > 'Options' > 'Options' > 'Advanced' >'General' tab
• section: 'Advanced Configuration'
• uncheck: 'Use hardware acceleration when available'
• click on OK

see image below as guide.

Restart Thunderbird (not in 'Safe Mode') and report back on results.

Thank you again Toad-Hall for your help.At least I can now open Thunderbird in safe mode quicker following your advice.However,when I went through the Menu sequence you describe,I found that the "Use hardware acceleration when available" was not checked,so could not be unchecked.

I have donated $20 to Thunderbird.

My son has just been for a visit and he solved the problem in less than 5mins.What had happened was that the update had altered the settings on my account,my son quickly rectified this.All is now fine!