I have installed fresh Ubuntu 12.04 or you have upgraded your system from earlier version of Ubuntu to latest release Ubuntu 12.04. Once you rebooted your system now you are getting this error message:
The System is running in low graphics mode, Your Screen, graphics card,and input device settings could not be detected correctly. You will need to configure this yourself.
This is more less related to your ATI graphics card. So far what I have seen only systems with ATI different models graphics cards are getting this error message upon clean install or upgrade from older version to latest version of Ubuntu.
How do we fix it?
There is simple fix for this issue. Once you get the error on your screen press ALT+CTRL+F1, once in new screen type/run these commands
sudo apt-get update sudo apt-get purge flglrx sudo reboot
The message should be gone, if not there is good chnage that you have also trouble with gdm and you can fix it in these steps:
Again press ALT+CTRL+F1 and run these commands
sudo apt-get install gdm sudo service gdm restart
As far as I know and tested, these two methods helped to solve the issue on majority of Ubuntu boxes.