Hello Folks. If you have been using Lightning 2.3b1 with a localized version of Thunderbird, you probably had troubles with undefined entities. This happened due to a glitch with the Mozilla localization dashboard, the wrong changeset was used.
I have just uploaded Lightning 2.3b2, which should fix the issue. As always, you can download beta versions from the addons.mozilla.org site in the “Developer Channel” box. If you have previously installed a beta, you should get the update via automatic updates.