Tente isto:
Executar em um terminal:
sudo -i
apt-get update
apt-get install software-properties-common
apt-get dist-upgrade
apt-get install xserver-xorg xserver-xorg-core xfonts-base xinit x11-xserver-utils x11-apps x11-session-utils x11-utils xinput xorg lightdm lightdm-gtk-greeter oxygen-icon-theme flashplugin-installer gstreamer0.10-ffmpeg libcurl3 libnotify4 libtag1-vanilla dkms gvfs gvfs-backends policykit-1 udisks2 synaptic fluxbox fluxconf idesk rox-filer
dpkg --configure -a
apt-get autoremove
apt-get clean
reboot
Editado: instalação mínima do fluxbox
Executar em um terminal:
sudo -i
apt-get update
apt-get dist-upgrade
apt-get install xorg gvfs gvfs-backends policykit-1 udisks2 fluxbox fluxconf idesk rox-filer
dpkg --configure -a
apt-get autoremove
apt-get clean
reboot