Something corrupted with system, update failure and movie player problemss

I cannot play an .avi movie, cannot delete and re-install Movie Player, and a software update just failed. Also, I always accept update and todays failed to install. My system: Ubuntu- the Karmic Koala on a IBM T23 laptop.

I don't have clue how to fix these problems. I assume they are somehow related. I'll attach some info about them that may be more help. I have tried to delete and re-install and it seems this is not working using software center and synaptic.

Any test or applications available to check my software? Can you help? I can follow directions but do not know the jargon and processes like you do so be sure to start at the point of assuming I don't have a clue ( I don't) and we'll get it fixed, I'll bet.

Movie Player returns this comment after a search for a suitable plugin:
The requested plugins are:

ITU H.264 decoder cannot be found

Mplayer Info:
E: imagemagick: subprocess installed post-installation script returned error exit status 2
E: libavutil-extra-49: subprocess installed post-installation script returned error exit status 2
E: libopenjpeg2: subprocess installed post-installation script returned error exit status 2
E: libavcodec-extra-52: dependency problems - leaving unconfigured
E: libavdevice52: dependency problems - leaving unconfigured
E: libavfilter0: dependency problems - leaving unconfigured
E: ffmpeg: dependency problems - leaving unconfigured
E: libsox1a: subprocess installed post-installation script returned error exit status 2
E: libsox-fmt-base: dependency problems - leaving unconfigured
E: libsox-fmt-alsa: dependency problems - leaving unconfigured
E: sox: dependency problems - leaving unconfigured
E: libnetpbm10: subprocess installed post-installation script returned error exit status 2
E: netpbm: dependency problems - leaving unconfigured
E: dvd-slideshow: dependency problems - leaving unconfigured
E: mplayer: dependency problems - leaving unconfigured
E: videotrans: dependency problems - leaving unconfigured
E: qdvdauthor: dependency problems - leaving unconfigured
E: transcode: dependency problems - leaving unconfigured
E: subtitleripper: dependency problems - leaving unconfigured
E: mplayer-nogui: dependency problems - leaving unconfigured
E: smplayer: dependency problems - leaving unconfigured
E: smplayer-themes: dependency problems - leaving unconfigured
E: smplayer-translations: dependency problems - leaving unconfigured