I finally managed to get rid of the duplicate local folders by manually
removing the offending files in my "Local Mail" folder for it (making
sure to keep the ones for the folder that actually had the mails in it).
That seems to have fixed the startup crash for me.
My only theory - and this is just wild speculation - is that this mail
folder dated from some point before I switched to an UTF-8 locale, so it
still used Latin-1 as character encoding for the file name. The old
Thunderbird accepted this, at least as long as I didn't try to rename
the folder. Apparently the new Thunderbird did not.
That's as far as I'm going to pursue this. I wish Thunderbird would
handle this case more gracefully, but maybe it will at least help
someone else with the same problem.
Torbjörn Andersson
