I have also problems after the update yesterday (Sept 19). I have
I have Thunderbird 24.0 from the repositories.
$ lsb_release -a
No LSB modules are available.
Distributor ID: Ubuntu
Description: Ubuntu 12.04.3 LTS
$ uname -a
Linux ssd-grund 3.2.0-53-generic-pae #81-Ubuntu SMP Thu Aug 22 21:23:47 UTC 2013 i686 i686 i386 GNU/Linux
The window to write letters (or reply to letters) is borked. There is no cursor, and although it is focused, the active window is still the main Thunderbird window, so I can't write anything. This happens after running Thunderbird for a while, and I have to close and re-open Thunderbird to be able to write a letter again.
I'm reporting it at Launchpad as