apt-get upgrade fails for X11 due to some strange templates error

Question

I am using Ubuntu 10.04.4 LTS on my DELL Vostro 1400 laptop.
Today afternoon when i ran sudo apt-get upgrade i got a error.

Googled for it, but there was no particular workarounds suggested for it.
Heres the error:

ubuntu@ubuntu-laptop:~$ sudo apt-get -f install
Reading package lists... Done
Building dependency tree       
Reading state information... Done
0 upgraded, 0 newly installed, 0 to remove and 280 not upgraded.
2 not fully installed or removed.
After this operation, 0B of additional disk space will be used.
Setting up x11-common (1:7.6+8~bpo60+1) ...
Template parse error near `Choices-sr@latin.UTF-8: Samo glavni korisnik, Samo za korisnike konzole, Svako', in stanza #1 of /var/lib/dpkg/info/x11-common.templates
dpkg: error processing x11-common (--configure):
 subprocess installed post-installation script returned error exit status 9
dpkg: dependency problems prevent configuration of xserver-common:
 xserver-common depends on x11-common; however:
  Package x11-common is not configured yet.
dpkg: error processing xserver-common (--configure):
 dependency problems - leaving unconfigured
No apport report written because the error message indicates its a followup error from a previous failure.
Errors were encountered while processing:
 x11-common
 xserver-common
E: Sub-process /usr/bin/dpkg returned an error code (1)
ubuntu@ubuntu-laptop:~$

Any ideas on what could be the issue?

Answer 1

I found the cause, it was due to squeeze-backports entry in the sources.list.
Seems un compatible DEBs were being installed
Removed the entry.
And Re-Ran update, but still apt-get upgrade gave same error.

Then after a lot of meddling with commands, i ran sudo aptitude remove x11-common
It proposed a solution to downgrade x11.

The following actions will resolve these dependencies:

Downgrade the following packages:
x11-common [1:7.6+8~bpo60+1 (now) -> 1:7.5+5ubuntu1 (lucid)]

Score is -9979

Accept this solution? [Y/n/q/?] 

Gave 'Y' and it resolved the mismatch.
Later i ran apt-get upgrade which installed the latest deb of x11 for Ubuntu.
All is well now :D