Some more testing:
No (this) problem with opensource radeon driver.
Problem exists also with gdm (finally got it working when removed automatic login, otherwise hang in checking battery -in desktop-).
So it's not lightdm (only) and seems to be related to fglrx. (Also tried with latest version from AMD with same result.)
Currently workaround seems to be ctrl-alt Fn (but what Fn?) or logging out when leaving.
Next I will try to change gnome screensaver to xscreensaver (but I don't expect much...)
Some more testing:
No (this) problem with opensource radeon driver.
Problem exists also with gdm (finally got it working when removed automatic login, otherwise hang in checking battery -in desktop-).
So it's not lightdm (only) and seems to be related to fglrx. (Also tried with latest version from AMD with same result.)
Currently workaround seems to be ctrl-alt Fn (but what Fn?) or logging out when leaving.
Next I will try to change gnome screensaver to xscreensaver (but I don't expect much...)