Email as a task in Thunderbird does not reference the correct email....
If you use "Open messages in: An existing message window" Preferences->Advanced-> Reading & Display.
I tested this multiple times and, like many, I use TB in existing window because I do not want 100 open windows or tabs when I'm doing mail. Unfortunately, it appears that adding an email as a task is dependent upon the other options and, while I can add a task, it will always reference the last email from testing one of the other views. I would be incredibly grateful if you would fix this as I love your program and must continue to use "existing message window"
Currently running TB 17.0.6 on OSX 10.8.3