Is this problem happened when you edited HTML mail with embeded image?
If so, this may related to bug 532395 and Comment 99 may help you.
Invisibility of Draft edit window component may caused by broken XUL cache.
If that caused by broken XUL cache, you could purge XUL cache with the following plans:
From Terminal, execute the following command (If you install Tenfoubird in /Application/Tenfourbird/):
/Application/Tenfourbird/Contents/MacOS/bin/thunderbird -purgecaches
One of a such addon is Restartless Restart.
Procedures of purging XUL cache with Restartless Restart is:
To detect what happend on your Tenfourbird, I need more information of these problems:
Regards.
TenFourBird seems to have gone off the rails somewhere. I was using 17.0.11, and kept having trouble with writing a long e-mail. TenFourBird kept trying to attach something where I had no attachments. In the process of that, it declined to update or save a draft. It lost my work. I downloaded 24.3.0 and installed it. Now I can't even see my saved draft to edit it. All I get when I click on the "Edit" button is the header bar with the red-orange-green balls on the left. The rest is invisible.
I'm going to move my e-mail files to another computer with Win 7 & 8 so I can get my work done and stay in touch with people. I'll give up on TenFourBird if this isn't fixed.