I had the same problem: after the upgrade when logging the monitor turns off and on several times but without show login screen. I solved downgrading xserver-xorg-video-ati and xserver-xorg-video-radeon with versions downloaded from:
https://launchpad.net/ubuntu/+archive/primary/+sourcepub/944871/+listing-archive-extra
I have a Sapphire Radeon 4850:
01:00.0 VGA compatible controller: ATI Technologies Inc RV770 [Radeon HD 4850]
Next are some logs.
P.S. in xorg log I read
(II) LoadModule: "ati" (WW) Warning, couldn't open module ati (II) UnloadModule: "ati" (EE) Failed to load module "ati" (module does not exist, 0)
I had the same problem: after the upgrade when logging the monitor turns off and on several times but without show login screen. I solved downgrading xserver- xorg-video- ati and xserver- xorg-video- radeon with versions downloaded from:
https:/ /launchpad. net/ubuntu/ +archive/ primary/ +sourcepub/ 944871/ +listing- archive- extra
I have a Sapphire Radeon 4850:
01:00.0 VGA compatible controller: ATI Technologies Inc RV770 [Radeon HD 4850]
Next are some logs.
P.S. in xorg log I read
(II) LoadModule: "ati"
(WW) Warning, couldn't open module ati
(II) UnloadModule: "ati"
(EE) Failed to load module "ati" (module does not exist, 0)