ubuntu synaptic manager BROKEN 문제

시냅틱 메니져를 실행시키면

libx11-6이 broken 되어 있다는 메세지가 나옵니다.

reinstall을 해보려고 했으나 에러 메시지가 나오면서 안되는 군요...

아래와 같은 시도를 해보았습니다.

root@ieoi:~ # apt-get check
Reading package lists... Done
Building dependency tree... Done
You might want to run `apt-get -f install' to correct these.
The following packages have unmet dependencies:
  libx11-6: Depends: x11-common (> 4.3.0) but it is not installed
E: Unmet dependencies. Try using -f.

root@ieoi:~ # apt-get -f install
Reading package lists... Done
Building dependency tree... Done
Correcting dependencies... Done
The following extra packages will be installed:
  x11-common
The following NEW packages will be installed:
  x11-common
0 upgraded, 1 newly installed, 0 to remove and 693 not upgraded.
11 not fully installed or removed.
Need to get 0B/992kB of archives.
After unpacking 1520kB of additional disk space will be used.
Do you want to continue [Y/n]? y
WARNING: The following packages cannot be authenticated!
  x11-common
Install these packages without verification [y/N]? y
debconf: unable to initialize frontend: Dialog
debconf: (Dialog frontend will not work on a dumb terminal, an emacs shell buffer, or without a controlling terminal.)
debconf: falling back to frontend: Readline

Preconfiguring packages ...
(Reading database ... 76497 files and directories currently installed.)
Unpacking x11-common (from .../x11-common_6.8.2.dfsg.1-9_all.deb) ...
/var/lib/dpkg/tmp.ci/preinst: line 914: [: : integer expression expected
dpkg: error processing /var/cache/apt/archives/x11-common_6.8.2.dfsg.1-9_all.deb (--unpack):
 trying to overwrite `/etc/X11/Xsession', which is also in package xorg-common
dpkg-deb: subprocess paste killed by signal (Broken pipe)
Errors were encountered while processing:
 /var/cache/apt/archives/x11-common_6.8.2.dfsg.1-9_all.deb
E: Sub-process /usr/bin/dpkg returned an error code (1)

위와 같은 문제를 어떻게 해결해야 할까요? 도움 부탁합니다.