ress ctrl+alt+f1 to drop to a shell prompt, and type:
sudo apt-get install gdm
http://download.gamblis.com/search/wifi-hp-pavilion-g6/
Here is the link to the instructions I used:
https://atinfinity.wordpress.com/2011/05/21/ralink-rt5390-wi-fi-driver-on-ubuntu-11-04/
NOTE: use version V.2.4.0.4 – I could not get the Ralink V 2.5.0.3 to work with Ubuntu 11.04.
I am reproducing the steps here (with some of my own additions to save you some time) as you will have to redo part or all of them per the Warning that follows the list:
WARNING: DO NOT ERASE the extracted folder after installation – You will have to redo the Ralink Install whenever you get a new Linux generic update so make sure you keep the Ralink extracted folder IN YOUR OWN AREA, and simply redo steps 4, and 6-8.
Reboot and set up a wireless connection to your network. You may have to reboot again to make it work
http://www.avasys.jp/lx-bin2/linux_e/spc/DL1.do