Uninstall Lightning via the Add-Ons Manager. Restart Thunderbird. Re-install Lightning if it's needed.

Prairiebuoy did this solve your problem?

christ1 said

Uninstall Lightning via the Add-Ons Manager. Restart Thunderbird. Re-install Lightning if it's needed.

M ink end shows no add-ons, so lightning could not be removed. I started the program in safe mode (which, as I understand, would not initiate any add-ons) and it remains unresponsive. If I right click an inbox and select "open in a new tab, the inbox becomes available in the new tab but closes with the tab and I still cannot write new messages or open attachments.

No add"one show in the menu and program remains unresponsive in safe mode

No add'ons show on the menu and the program remains unresponsive in safe mode.

Can you post your Troubleshooting Information? At the top right of the Thunderbird window, click the menu button , then select Help > Troubleshooting Information. Press the Copy text to clipboard button and paste the information into your reply.

Thanks christ1, Here is the troubleshoot info. Looks like the lightning add-on is there. Now, if i can just figure out how to get rid of it... I tried the restart without add-on button in help, but to no avail.

 Application Basics

   Name: Thunderbird
   Version: 38.6.0
   User Agent: Mozilla/5.0 (Windows NT 6.1; WOW64; rv:38.0) Gecko/20100101 Thunderbird/38.6.0
   Profile Folder: Show Folder

             (Local drive)
   Application Build ID: 20160211132445
   Enabled Plugins: about:plugins
   Build Configuration: about:buildconfig
   Memory Use: about:memory

 Mail and News Accounts
   account2:
     INCOMING: account2, , (none) Local Folders, plain, passwordCleartext

   account8:
     INCOMING: account8, , (imap) imap.gmail.com:993, SSL, OAuth2
     OUTGOING: smtp.gmail.com:465, SSL, OAuth2, true

   account9:
     INCOMING: account9, , (imap) mail.usask.ca:143, alwaysSTARTTLS, passwordCleartext
     OUTGOING: mail.usask.ca:587, alwaysSTARTTLS, GSSAPI, true

 Crash Reports
   http://crash-stats.mozilla.com/report/index/bp-38578590-ffca-4d95-9cab-d2b652160226 (26/02/2016)

 Extensions
   Lightning, 4.0.6, true, {e2fda1a4-762b-4020-b5ad-a41df1933103}

 Important Modified Preferences

   Name: Value

     browser.cache.disk.capacity: 358400
     browser.cache.disk.smart_size_cached_value: 358400
     browser.cache.disk.smart_size.first_run: false
     browser.cache.disk.smart_size.use_old_max: false
     extensions.lastAppVersion: 38.6.0
     font.name.monospace.el: Consolas
     font.name.monospace.tr: Consolas
     font.name.monospace.x-baltic: Consolas
     font.name.monospace.x-central-euro: Consolas
     font.name.monospace.x-cyrillic: Consolas
     font.name.monospace.x-unicode: Consolas
     font.name.monospace.x-western: Consolas
     font.name.sans-serif.el: Calibri
     font.name.sans-serif.tr: Calibri
     font.name.sans-serif.x-baltic: Calibri
     font.name.sans-serif.x-central-euro: Calibri
     font.name.sans-serif.x-cyrillic: Calibri
     font.name.sans-serif.x-unicode: Calibri
     font.name.sans-serif.x-western: Calibri
     font.name.serif.el: Cambria
     font.name.serif.tr: Cambria
     font.name.serif.x-baltic: Cambria
     font.name.serif.x-central-euro: Cambria
     font.name.serif.x-cyrillic: Cambria
     font.name.serif.x-unicode: Cambria
     font.name.serif.x-western: Cambria
     font.size.fixed.el: 14
     font.size.fixed.tr: 14
     font.size.fixed.x-baltic: 14
     font.size.fixed.x-central-euro: 14
     font.size.fixed.x-cyrillic: 14
     font.size.fixed.x-unicode: 14
     font.size.fixed.x-western: 14
     font.size.variable.el: 17
     font.size.variable.tr: 17
     font.size.variable.x-baltic: 17
     font.size.variable.x-central-euro: 17
     font.size.variable.x-cyrillic: 17
     font.size.variable.x-unicode: 17
     font.size.variable.x-western: 17
     gfx.direct3d.last_used_feature_level_idx: 0
     mail.openMessageBehavior.version: 1
     mail.winsearch.firstRunDone: true
     mailnews.database.global.datastore.id: ea7d6f33-f0bb-4ba2-bfd1-2742d48dc28
     mailnews.database.global.views.conversation.columns: {"threadCol":{"visible":true,"ordinal":"1"},"flaggedCol":{"visible":true,"ordinal":"3"},"attachmentCol":{"visible":false…
     network.cookie.prefsMigrated: true
     network.predictor.cleaned-up: true
     places.database.lastMaintenance: 1456761784
     places.history.expiration.transient_current_max_pages: 104858
     plugin.importedState: true

 Graphics

     Adapter Description: Intel(R) HD Graphics Family
     Vendor ID: 0x8086
     Device ID: 0x0a16
     Adapter RAM: Unknown
     Adapter Drivers: igdumdim64 igd10iumd64 igd10iumd64 igdumdim32 igd10iumd32 igd10iumd32
     Driver Version: 10.18.10.3412
     Driver Date: 1-29-2014
     Direct2D Enabled: false
     DirectWrite Enabled: false (6.2.9200.17568)
     ClearType Parameters: ClearType parameters not found
     WebGL Renderer: false
     GPU Accelerated Windows: 0

     AzureCanvasBackend: skia
     AzureSkiaAccelerated: 0
     AzureFallbackCanvasBackend: cairo
     AzureContentBackend: cairo

 JavaScript

 Incremental GC: 1

 Accessibility

   Activated: 0
   Prevent Accessibility: 0

 Library Versions

     Expected minimum version
     Version in use

     NSPR
     4.10.10
     4.10.10

     NSS
     3.19.2.2 Basic ECC
     3.19.2.2 Basic ECC

     NSS Util
     3.19.2.2
     3.19.2.2

     NSS SSL
     3.19.2.2 Basic ECC
     3.19.2.2 Basic ECC

     NSS S/MIME
     3.19.2.2 Basic ECC
     3.19.2.2 Basic ECC

Looks like the lightning add-on is there.

Indeed. I'd just be curious why you stated three time before it wouldn't be.

Start Thunderbird in safe mode. http://kb.mozillazine.org/Safe_mode Then follow the instructions from the post above. https://support.mozilla.org/en-US/questions/1112745#answer-851679

You will have to forgive my elementary level of familiarity with Thunderbird and with computer troubleshooting. I appreciate your patience.

The difficulty I am having is that the link in Thunderbird Help to the add-on manager (the blue jigsaw puzzle piece) does not respond, so there is no indication of which add-ons may be present, and there is no option for removing add-ons. The situation is the same when I start the computer in safe mode. I am there for perplexed about how to actually remove lightning from my unresponsive program.

You'll need to start Thunderbird in safe mode as per the article posted above.

Thank you - this has fixed my problem! My mistake was to not read the fine print, so I had re-started my computer in safe mode rather than simply re-starting Thuderbird progrm in safe mode. Your assistance is much appreciated!!