firefox crash when showing general preferences, downloads or downloading a file

had a problem recenty that downloading a file, showing the default preferences or showing the downloads dialog made firefox quit unexpectedly.
don’t know what happened or why exactly but it seems to be a problem with gnome-vfs.

my solution (so far with no side effects) is to comment this line

#file: file

ind the /etc/gnome-vfs-2.0/modules/default-modules.conf file.