And to those of you that are now unable to start maemo mapper at all, resetting your gconf settings may help you. From an xterm:

gconftool-2 --recursive-unset "/apps/maemo/maemo-mapper"

NOTE: You will, of course, lose all your previously saved settings, although your maps will still remain where you had previously downloaded them (in order to see them, you may have to set your repository's cache dir after resetting your gconf settings).

If you do end up resetting your settings, let me know if you experience further segfaults or other errors. It is possible that some of these issues are cropping up due to maemo-mapper 1.2's attempt to "upgrade" from the 1.1 settings layout.