Rated 5 out of 5 stars
Happiness was fleeting indeed :)
Mnenhy 0.8.6 worked with Thunderbird until TB was updated to version 31. At least the custom headers feature of Mnenhy 0.8.6 (the one I use most) doesn't work anymore with Thunderbird 31.
So we're stuck with TB 24.* until Mnenhy's developer can update it to work with the latest versions of Thunderbird (crossing fingers! ;) )
Anyway, I'm keeping the five stars for this review because Mnenhy is such a great add-on.
I can confirm that the new version of Mnehny (0.8.6) works perfectly with Thunderbird 24. Thanks, Karsten!!!!