Hi Folks,
Recently I came around this problem, that whenever I used to update my linux (kernel) which is currently now (3.2.0-43-generic-pae), on restarting my machine after updation my machine would always boot to linux command line asking for the userid and password. It would not boot to the GUI. On searching quite a bit I found out that this problem was due to a problem with graphics card driver update. The kernel update was unable to load properly the previously installed driver and showed a message no graphics driver is installed. To overcome this problem and boot to your GUI simple steps have to be followed. These steps simply remove any installed graphics driver which cause problems and u can later install the graphics card driver specific to your machine later on when u boot to GUI.
Step 1) when u boot to command line enter your user id and password correctly. Then enter the following commands line by line.
sudo sh /usr/share/ati/fglrx-uninstall.sh
sudo apt-get remove --purge fglrx fglrx_* fglrx-amdcccle* fglrx-dev*
after these commands run successfully perform a reboot using
sudo reboot
Then u shall be able to boot into your GUI. Now u need to install your graphics card driver again. If you tend to have a AMD Radeon HD 6300 series graphics card u can follow how to install post <here>.
Researching Wirelessly 