Comment 59 for bug 443080

My system was restored and I was running Karmic for a week. Now, the same problem arises. I again tried to follow your steps (below). Can you please tell me what should be removed or what causes the problem that should be removed when I'm in the problematic install (mount from disk - Solution mentioned by Ernst)

I don't think there are packages that provide faulty repos. Also, 'sudo gedit /ubuntu/ etc/apt/ sources. list' command opens a blank file.

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Boot with the liveCD/USB and do:

sudo -s -H
mkdir /media/ubuntu
# system partition:
mount /dev/sda5 /media/ubuntu
#/home partition:
mount /dev/sda7 /media/ubuntu/home
mount --bind /dev/ /media/ubuntu/dev
mount --bind /dev/pts /media/ ubuntu/ dev/pts
mount --bind /dev/shm /media/ ubuntu/ dev/shm
chroot /media/ubuntu
mount -t sysfs sysfs /sys
mount -t proc proc /proc
dhclient

Now, you are in your problematic install.
You can use "sudo aptitude remove ....." to remove a certain package, "sudo
nano /etc/apt/ sources. list" to remove repositories who provide faulty
packages (or sudo gedit /ubuntu/ etc/apt/ sources. list on the host, which is
more convenient for most people), "sudo aptitude install <package>/karmic to
downgrade a package to karmic.