Error message using truecrypt in mint mate
When double clicking to open a volume from the Truycrypt gui, it calls nautilus. Nautilus may not be installed on your system or having it running alongside caja is yuck. There is no easy way to configure which file manager to be used in the preferences.
Since caja and nautilus have similar command line arguments a simple symbolic link is possible
sudo ln -s /usr/bin/caja /usr/bin/nautilus