Xorg 7.2 with Radeon free drivers breaks mergedfb!!!
Thats right. My dual head display stopped spaning both screens with mergedfb and I was presented with the dreadful cloned screens. yuk!
I kept recieving errors in my xorg log about no modes being found for crt2. I was puzzled by this because I am using the eaxct same xorg.conf file from Debian Etch and Xubuntu Fiesty which worked perfectly.
After 2 weeks of researching this and playing and configuring and pulling hair out I finally found the problem...
Something was majorly wrong with that package and caused mergedfb to disable.
I upgraded this package from Debian Experimental repo and everything works fine now.
I'm not sure about all distros, but I do know this fix works for K/X/Ubuntu and Debian Lenny/Sid.
My mergedfb works again as its supposed to! Just thought I would mention this since its barely mentioned anywhere else on the net...