On taskbar I get a red warning icon that "A problem occurred when checking for the updates" When I click on Show Updates I get "Failed to the load the package list" in the details is the following: An unresolvable problem occurred while initializing

What is the output of:

head /etc/apt/sources.list

Thanks

The message tells you where the problem is..

" E:Malformed line 3 in source list /etc/apt/sources.list (dist parse)"

So , the 3rd line is /etc/apt/sources.list is malformed .. and you must correct the line manually.

Open the file as administrator with the command below

gksudo gedit /etc/apt/sources.list

find the 3rd line and correct it.

If you don't know or you are not sure what to correct ,then give here the results as @actionparsnip suggested.

Thanks

There is no list after I command "gksudo gedit/etc/apt/sources.list

It wants a space between gedit and /

gksudo gedit /etc/apt/sources.list

output appeared in text editor type like:
deb http://archive.ubuntu.com/ubuntu/ quantal main restricted universe multiverse
deb http://security.ubuntu.com/ubuntu/ quantal-security main restricted universe multiverse
deb http://archive.canonical.com/ partner
deb-src http://archive.canonical.com/ partner
deb http://archive.ubuntu.com/ubuntu/ quantal-updates main restricted universe multiverse
which line has to change?

Change

deb http://archive.canonical.com/ partner
deb-src http://archive.canonical.com/ partner

To

deb http://archive.canonical.com/ quantal partner
deb-src http://archive.canonical.com/ quantal partner

and then?

Thanks actionparsnip, that solved my question.

head /etc/apt/sources.list:
i got this o/p

# deb cdrom:[Ubuntu 10.04 LTS _Lucid Lynx_ - Release i386 (20100429)]/ lucid main restricted
# See http://help.ubuntu.com/community/UpgradeNotes for how to upgrade to
# newer versions of the distribution.

deb http://ubuntu.pesat.net.id/archive/ precise main restricted
deb-src http://ubuntu.pesat.net.id/archive/ precise main restricted

## Major bug fix updates produced after the final release of the
## distribution.
deb http://ubuntu.pesat.net.id/archive/ precise-updates main restricted

run:

gksudo gedit /etc/apt/sources.list

remove the top 3 lines:

# deb cdrom:[Ubuntu 10.04 LTS _Lucid Lynx_ - Release i386 (20100429)]/ lucid main restricted
# See http://help.ubuntu.com/community/UpgradeNotes for how to upgrade to
# newer versions of the distribution.

Save the new file, close gedit and run:

sudo apt-get update

Is it now smooth?

Thanks

i got this as the o/p aftr i deleted the first three lines:

E: Type '<!DOCTYPE' is not known on line 1 in source list /etc/apt/sources.list.d/playonlinux.list
E: The list of sources could not be read.

sudo rm /etc/apt/sources.list.d/playonlinux.list
sudo apt-get update

done now!!!..
thank u soo much..