Thunderbird is way out of sync with Firefox in terms of setting default applications for opening attachments MIME times. The latest one I noticed is that it tries to open *.docx (Word 2007+) files with the Archive Manager rather than LibreOffice, but I've noticed in the past that it can't open *.wmv files either, and opens *.doc files with KWrite even though LibreOffice is installed. Please change the default apps to match the Firefox selections, which are far more sane.
you have already report this bug *** This bug has been marked as a duplicate of bug 2027 ***
Status: NEW => RESOLVEDResolution: (none) => DUPLICATE
I thought I had, but a search on "thunderbird" didn't show it, so I figured it must be from back in the cooker days...