case closed, another opened... it was due to xserver-xorg-driver-ati-6.6.0.0 (with the preferdb visual patch), downgraded to 6.5.7.3 and suprised as i am, it's working again.
-- The whole system freeze if I scroll up/down using the bar https://launchpad.net/bugs/52508 -- desktop-bugs mailing list desktop-bugs@lists.ubuntu.com https://lists.ubuntu.com/mailman/listinfo/desktop-bugs
