ubuntu14.04, stuck at login page

If you reboot to an older kernel is it ok?

no, its same problem with older kernels...

If you use 'advanced options - drop to root shell' you have to remount the hard drive as read-write before you can do any change.

mount -o rw,remount /

yes, I used sudo mount -o remount,rw / but when i use apt-get update after this, it fails and give msgs like, 'failed to fetch .... could not resolve '......'' any idea how to get around it... thanks..

'failed to fetch .... could not resolve ' is a different problem. It show that the system is not able to connect to the internet.
What network connection do you normally have? WLAN? Can you temporarily connect your system to the router with a LAN cable?

Another possibility would be trying to work in a virtual console.

Please describe exactly what there is happening when you try booting normally.

Pressing ctrl-alt-F1 on the login page should open a virtual console (somewhat looking like a full-screen terminal window, requesting username and password for logging in). Can you log in there?

sorry for the late reply... while booting normally, i get to the ubuntu logo screen and then remain stuck there... i tried virtual console, i am able to login there.. through virtual console, i tried apt-get update, upgrade, dist-upgrade and all, but it didn't solve the problem... when i tried 'sudo apt-get build-dep xorg' and 'sudo dpkg-reconfigure xserver-xorg', i get the msg 'xserver-xorg is broken or not fully installed'...

In the virtual console, what output do you get on

sudo dpkg --audit

What error messages do you get for

sudo apt-get install -f

for 'sudo dpkg --audit', i don't get any msg... for 'sudo apt-get install -f' also, i don't get any error msg, it get executed with msg '0 upgraded, 0 new installed, 0 to remove and 0 not upgraded'

Ok, then your package management system seems to be in a consistent state, and messages like 'xserver-xorg is broken or not fully installed' should not show up.

Does one of the following commands result in error messages:

sudo apt-get update
sudo apt-get upgrade
sudo apt-get dist-upgrade
sudo apt-get install ubuntu-desktop

for 'sudo apt-get update', i get 'W: failed to fetch cdrom://ubuntu 14.04 ......... unable to find expected entry 'main /binary-amd64/packages' in Release file (wrong sources.list entry of malformed file)
E: some index files failed to download. they have been ignored or old ones used instead.'

for 'sudo apt-get upgrade', no error msg..

for 'sudo apt-get dist-upgrade', no error msg...

for 'sudo apt-get install ubuntu-desktop', error msg: 'some packages could not be installed. this may mean that you have requested an impossible situation or if you are using the unstable distribution that some required packages have not yet been created or been moved out of Incoming.
The following information may help to resolve the situation:

the following packages have unmet dependencies:
ubuntu-desktop: Depends: software-centre but it is not going to be installed.
                                 Depends: ubuntu-release-upgrader-gtk..................
                                ....................................

E: unable to correct problems, you have broken packages.'

Apparently there are really some dependency problems that prevent correct installation and upgrade of packages.

I see two possibilities:
1. restart from scratch with a new installation
2. try getting the dependency problems resolved.

ad 1: Do you have lots of data that you want to keep, or is it easily possible to do a new installation?

ad 2: The first steps that would be required for getting the dependency problems solved:
In the virtual console issue the command
sudo nano /etc/apt/sources.list
This should open an editor with the sources.list configuration file loaded.
Put a hash sign '#' in front of the top lines that refer to the CDrom (change "deb cdrom:..." into "# deb cdrom:...")
save the file (ctrl-o) and close the editor (ctrl-x), then re-issue the command
sudo apt-get update
Are there any further error messages?

How many broken dependencies are shown for the command
sudo apt-get install ubuntu-desktop

Do you have lots of PPAs and foreign sources enabled?
How may files are in the directory
ls /etc/apt/sources.list.d

i can transfer the data through liveusb, so thats not a problem.. i have to fine tune all the setting and all... moreover, i wanted to understand... whats just went so wrong that it totally irrecoverable.. so will try the 2nd option first and let you know...