Installed the new version of thunderbird this week which went well apart from the dictionary going mental. Not to worry easily fixed by copying the myspell files to a new directory as outlined in the post below.
After installing the new release thunderbird 126.96.36.199 (update from thunderbird 1.5) the german dictionary does not work and the add on of the dictionary does not work too. I created a new directory ..\Mozilla Thunderbird\dictionaries and copied the old files *.dic and *.aff from ..\Mozilla Thunderbird\components\myspell to the new directory.
this is in the “Program files” folder no the application settings folder as I first thought. The dictionary files are not part of a user profile but installed as and extension to the app itself.