i have raring ringtail. I installed gnome a couple days ago. I try to install extensions but the site says I don't have the latest version. I type the command

sudo apt-get install gnome-shell

and I get this error

    Reading package lists... Done
Building dependency tree       
Reading state information... Done
gnome-shell is already the newest version.
0 upgraded, 0 newly installed, 0 to remove and 138 not upgraded.
1 not fully installed or removed.
After this operation, 0 B of additional disk space will be used.
Do you want to continue [Y/n]? y
Setting up initramfs-tools (0.103ubuntu0.7) ...
update-initramfs: deferring update (trigger activated)
Processing triggers for initramfs-tools ...
update-initramfs: Generating /boot/initrd.img-3.8.0-25-generic
cp: cannot stat ‘/module-files.d/libpango1.0-0.modules’: No such file or directory
cp: cannot stat ‘/modules/pango-basic-fc.so’: No such file or directory
E: /usr/share/initramfs-tools/hooks/plymouth failed with return 1.
update-initramfs: failed for /boot/initrd.img-3.8.0-25-generic with 1.
dpkg: error processing initramfs-tools (--configure):
 subprocess installed post-installation script returned error exit status 1
No apport report written because MaxReports is reached already
                                                              Errors were encountered while processing:
 initramfs-tools
E: Sub-process /usr/bin/dpkg returned an error code (1)

why?