"Zypper ref error" during (re)installation of few packages (e.g vlc)

I had installed various packages for multimedia content following the guides mentioned here: http://forums.opensuse.org/content/107-re-multi-media-restricted-format-installation-guide.html

But later on I found, all the softwares for playing media files got installed. And I uninstalled 'em one by one leaving back vlc. But to my surprise, while playing video files there was no audio, I must have deleted some important files too.
Now I am trying to reinstall those once again. But after refreshing zypper I am getting an error (as under):

babloo@linux-75vz:~> su
Password:
linux-75vz:/home/babloo # zypper ar -f Index of /suse/openSUSE_12.1/ packman
Adding repository ‘packman’ [done]
Repository named ‘packman’ already exists. Please use another alias.
linux-75vz:/home/babloo # zypper ar -f http://opensuse-guide.org/repo/12.1/ libdvdcss
Adding repository ‘libdvdcss’ [done]
Repository named ‘libdvdcss’ already exists. Please use another alias.
linux-75vz:/home/babloo # zypper ref
Repository ‘libdvdcss’ is up to date.
Repository ‘packman’ is up to date.
Repository ‘openSUSE-12.1-Non-Oss’ is up to date.
Repository ‘openSUSE-12.1-Oss’ is up to date.
Retrieving repository ‘openSUSE-12.1-Update’ metadata ]
File ‘repomd.xml’ from repository ‘openSUSE-12.1-Update’ is unsigned, continue? [yes/no] (no):

How can I get rid of this error?
Is there any way to install only vlc (rather than all the media players). The Step3 of the “Multi-media and Restricted Format Installation Guide” mentioned above installs all of the media players.
Thanks in advance.

There is currently a bug report on this
File ‘repomd.xml’ from repository ‘openSUSE-12.1-Update’ is unsigned, continue? [yes/no] (no):

You should choose No and wait for the fix. Which means for the moment the Update repo is out of action.

The multimedia guide is comprehensive, to ensure success in playback. Deviate from it by all means, but it will need user experience.

The oneclick option does give a much lighter install:
Restricted formats - openSUSE Community Wiki

Thanks.
Will wait for the bug to get fixed and install them later.