I am running 32-bit Ubuntu precise (12.04) and trying to set up dual monitors. I have 2 AMD/ATI Cayman XT [Radeon HD 6970] video cards in crossfire mode (if that makes a difference) and no proprietary drivers installed, but might have installed fglrx_12.104-0ubuntu_i386 driver, the output of the following command 'glxinfo | grep -i vendor' is this:
server glx vendor string: ATI
client glx vendor string: ATI
OpenGL vendor string: Advanced Micro Devices, Inc.

The problem is when I select the Display icon form the System Settings I get the following error:
Could not get screen information.
RANDR extension not present.

I can see the extension of my left desktop on my right except that I have to move my mouse to the left side of my left monitor which takes me to the right side of my right monitor. I would like to be able to just move the mouse from the left to right monitor through the center which is something I cannot do now. I tried downloading libxrandr2 version 2:1.3.2-2-ubuntu0.2 along with libxrandr2-dev libxrandr-dev libxrandr0-dev and x11proto-randr-dev thinking that that would solve the issue by it didn't. Any ideas what I should do?

I just had to purge all proprietary drivers and then reinstall them and now everything works.