Не устанавливается gnome-desktop-environment.В чём дело?

root@172947:~# apt-get -y install gnome
Reading package lists... Done
Building dependency tree
Reading state information... Done
Some packages could not be installed. This may mean that you have
requested an impossible situation or if you are using the unstable
distribution that some required packages have not yet been created
or been moved out of Incoming.
The following information may help to resolve the situation:

The following packages have unmet dependencies:
 gnome : Depends: gnome-core (= 1:3.4+7+deb7u1) but it is not going to be installed
         Depends: cheese (>= 3.4) but it is not going to be installed
         Depends: evolution (>= 3.4) but it is not going to be installed
         Depends: evolution-plugins (>= 3.4) but it is not going to be installed
         Depends: gedit (>= 3.4) but it is not going to be installed
         Depends: gnome-color-manager (>= 3.4) but it is not going to be installed
         Depends: gnome-documents (>= 0.4) but it is not going to be installed
         Depends: gnome-games (>= 1:3.4) but it is not going to be installed
         Depends: nautilus-sendto (>= 3.0) but it is not going to be installed
         Depends: gnome-orca (>= 3.4) but it is not going to be installed
         Depends: rygel-preferences (>= 0.14) but it is not going to be installed
         Depends: seahorse (>= 3.4) but it is not going to be installed
         Depends: totem (>= 3.0) but it is not going to be installed
         Depends: alacarte (>= 0.13.4) but it is not going to be installed
         Depends: gimp (>= 2.8) but it is not going to be installed
         Depends: gnome-media (>= 3.4) but it is not going to be installed
         Depends: gnome-tweak-tool (>= 3.4) but it is not going to be installed
         Depends: rhythmbox (>= 2.96) but it is not going to be installed
         Depends: shotwell but it is not going to be installed
         Depends: sound-juicer (>= 3.4) but it is not going to be installed
         Depends: gedit-plugins (>= 3.4) but it is not going to be installed
         Depends: gnome-applets (>= 3.4) but it is not going to be installed
         Depends: gnome-shell-extensions (>= 3.4) but it is not going to be installed
         Depends: rhythmbox-plugins but it is not going to be installed
         Depends: rhythmbox-plugin-cdrecorder but it is not going to be installed
         Depends: rygel-playbin but it is not going to be installed
         Depends: rygel-tracker but it is not going to be installed
         Depends: telepathy-gabble but it is not going to be installed
         Depends: telepathy-salut but it is not going to be installed
         Depends: totem-plugins but it is not going to be installed
         Recommends: gdebi but it is not going to be installed
         Recommends: nautilus-sendto-empathy but it is not going to be installed
E: Unable to correct problems, you have held broken packages.