I just started using Sabayon Linux instead of Ubuntu. Ubuntu went just stupid after changing to Unity (specially with my video cards), so I wanted to give a try to something else.
Downloaded Sabayon 10 and burned into a DVD, but everything became difficult after that. The ISO won't past the Start/Install Sabayon option in the boot screen. The dvd would stop spinning, my flashdrive (burned with dd_rescue) would turn off.
The solution was using Universal USB Installer for Windows http://www.pendrivelinux.com/universal-usb-installer-easy-as-1-2-3/ and I have to say, it works perfectly fine with every distro I tried (worked just better than unetbootin).
After installing the distro, I realize this was not gonna be a clean migration to Sabayon to my hardware; because the system just won't boot up, or at least the graphical interface.
During the boot, between the "Press Alt+F1" and "Press F2" for verbose mode, the display would show garbage and X would fail. Pressing Ctrl+Alt+F1 would send me to tty1 and there I could restart.
I only could boot in graphics mode pressing Alt+F1 and later F2 for verbose mode. Convenient huh? I wanted to see what had failed and when I do keep an eye on the system messages it would just work as normal.
But it looked like a stripped version of gnome. No effects, no beautiful interface. Something was wrong. So I started reading about it.
Finally, with some help of the sabayon irc channel I could fix it:
Installed xf86-video-ati drivers. An user told me flgrx is no longer supported in 4xxx series, so the best choice is going with the open source version.
# equo install xf86-video-ati
Set xorg-x11 as the primary open-gl interface
# eselect opengl set xorg-x11
And set the radeon driver in /etc/X11/xorg.conf
# nano /etc/X11/xorg.conf
It was before set with "ati". The same user told me this behavior was strange, the gpu-detector should select radeon, but it hasn't been an isolated case. And since "ati" would work nonetheless and start, people would use it but reporting glitches and performance issues.
The driver mismatch could be confirmed with:
# lspci -k
which in "VGA compatible controller" section, the kernel driver in use was in fact "radeon"
I hope this helps someone else with same problem.