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I’m hopeful lighting 1.5.2 comes out soon so this workaround won't be necessary
Roland Tanglao (Thunderbird Technical Support Lead) June 20, 2012 22:29

How to downgrade to Lightning 1.5.0 to workaround the "Invite Attendees" bug with TB 13 and Lightning 1.5.1

Hi All:

To fix the "Invite Attendees" bug with Lightning 1.5.1 and TB 13 (it appears to be Windows only, please let us know if you are experiencing it on Mac or Linux):

1. downgrade to Lightning 1.5.0 (instructions below)
WARNING: 1.5.0 is not available in all locales so you might have to use the English version


2. edit (if you are comfortable with a text editor) calendar-event-dialog.css as per:

The Lightning team is preparing an update to fix this but I don't know when it will be available; hopefully soon!

If you are technical, you can track progress in the bug tracking system by following bug 765530

How to downgrade to Lightning 1.5.0 from Lighting 1.5.1
(full details at: )

a)In your web browser go to:

Move your cursor down to "Version 1.5"
Beside it Click on "Download for Windows" (or Linux or Mac OS X depending on your OS) as per this screenshot for Windows (Linux and Mac are similar):

Save the file to your Downloads folder

b) In Thunderbird:
Tools | Add-ons | Get Add-ons | Click on the gear icon in Mac and Windows:

Gear icon looks like this on Linux:

and then
"Install add-on from file..."
Select the file you downloaded in a)
and click Open
c) Restart Thunderbird
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