Hi,
do you have your software sources download location set to "Main "?, check out the update guide and change the settings per the guide and then try updating again.
Do you have codecs installed?.
sudo apt-get install ubuntu-restricted-extras libxine2-all-plugins faac flac gstreamer0.10-plugins-ugly gxine libdvdread4 totem-mozilla icedax tagtool easytag id3tool lame nautilus-script-audio-convert libmad0 mpg321 libavcodec-extra
These are my own setting preferences, use at your own risk!.
AN IMPORTANT NOTE FOR LINUX BEGINNERS. WHEN YOU ARE IN RECOVERY MODE, THE KEYBOARD DEFAULTS TO US ENGLISH, IF YOU HAVE ANY OTHER LANGUAGE KEYBOARD OTHER THAN US ENGLISH, WHEN YOU TYPE "Y" (FOR "YES"), IT MIGHT SHOW UP AS A DIFFERENT LETTER, ON MY KEYBOARD I MUST PRESS THE "Z" KEY WHICH EQUATES TO "Y" AS I HAVE A GERMAN KEYBOARD, JUST PRESS "BACKSPACE" AND HIT A DIFFERENT KEY UNTIL YOU SEE THE "Y" SHOW UP!.