I have recently upgraded to Ubuntu 12.04 LTS without problems and installed Cinnamon following these instructions
There seems to be a problem with the ATI proprietary drivers and dual screen setups. I have a ATI Radeon HD 5450 graphics card. When I use the open source driver, I can easily setup my two screens with xinerama, but the performance is low. When I install the proprietary driver via the "additional drivers"-tool it is impossible to get both screens to work. Neither with xinerama nor withe the onboard tools. I either get thrown back to failsafe gnome session (which is unusable, because there are way to many panels loaded) or I get a cinnamon session with cloned screens.
I searched the web for some solutions but nothing helped. Does anyone have suggestions how to set this up?
display: :0 screen: 0 OpenGL vendor string: Advanced Micro Devices, Inc. OpenGL renderer string: ATI Radeon HD 5450 OpenGL version string: 4.2.11627 Compatibility Profile Context
Linux stefan-linux 3.2.0-27-generic #43-Ubuntu SMP Fri Jul 6 14:25:57 UTC 2012 x86_64 x86_64 x86_64 GNU/Linux
cinnamon --version Cinnamon 1.4.0
Thanks in advance!