Looks like you were half right about accessibility. >From the logs I found out this: gnome-session-binary[4732]: WARNING: Application 'at-spi-dbus- bus.desktop' failed to register before timeout appearing right after the black screen. Anyway I do have accessibility disabled (triple-checked) and it's weird that other gnome sessions work fine. What's even weirder is that it looks like my at-spi-dbus- bus.desktop already has that line not commented so the patch is not needed. For now, since I don't use it, I worked around the issue moving the at- spi-dbus-bus.desktop file out of the way. Thank you so much for your kind help, I guess I'll have to report to the gnome bugtracker for this issue :)
- Bug#812555: gnome-session-flashback (temporary) black... Massimo Martelli
- Bug#812555: gnome-session-flashback (temporary) ... Alberts Muktupāvels
- Bug#812555: gnome-session-flashback (tempora... Massimo Martelli
- Bug#812555: gnome-session-flashback (tem... Alberts Muktupāvels
- Bug#812555: gnome-session-flashback ... Massimo Martelli
- Bug#812555: gnome-session-flash... Alberts Muktupāvels
- Bug#812555: gnome-session-flash... Massimo Martelli
- Bug#812555: gnome-session-flash... Alberts Muktupāvels
- Bug#812555: gnome-session-flash... Massimo Martelli
- Bug#812555: gnome-session-flashback ... Dmitry Shachnev
- Bug#812555: gnome-session-flashback (temporary) black... Massimo Martelli
- Bug#812555: gnome-session-flashback (temporary) ... Alberts Muktupāvels
- Bug#812555: gnome-session-flashback (tempora... Massimo Martelli
- Bug#812555: gnome-session-flashback (tem... Alberts Muktupāvels
- Bug#812555: gnome-session-flashback ... Massimo Martelli