Whether I install torbrowser-launcher from Beowulf repository or
download it from www.torproject.org, I find that it insists on
saving files to no longer mounted drive.

When I browse other save locations, all locations are /dev/sdc, and
those locations are not accessible. I cannot write to the "save files
as" field in download preferences. When I set always ask where to
save, I can set the locationin preferences, but I'm not actually asked
where to save it.

Some time ago /dev/sdc was mounted, but not used for tor browser. I
could not find in what file the tor browser configuration is located.
I have firefox-esp installed, but it does not have the problem.

--
Haines Brown