I have a laptop HP Pavilion g6-1075er with Ubuntu 12.04 and AMD Radeon HD 6470M on board. I had default graphics configuration but some problems with xorg occurred. I had black screen, but I was able to "reset" graphics configuration to some workable state via recovery mode. But this state was slightly different from the default one (Alt+Tab didn't show same 3D selection, Alt+` doesn't work everywhere etc). So, I decided to revert it to default state. I checked this post http://ubuntuforums.org/showthread.php?t=1517170 and used the following commands:
sudo apt-get install --reinstall libgl1-mesa-glx libgl1-mesa-dri
sudo dpkg-reconfigure xserver-xorg
After rebooting I just get a black screen (in normal boot mode I think there is a nonblinking cursor also) and no login window. The same in recovery mode. So I can't enter any commands.
What can I do?
UPDATE: if I boot to Windows 7, hibernate and then boot to Ubuntu recovery mode, then I get the recovery menu.
By hibernating from Windows 7 and pressing cursor while loading Ubuntu I can get a TTY session. From there I tried to purge fglrx, install fglrx and many other things, but no effect so far.