After talking to Travis a bit, this is probably a fglrx 8.42 bug.... Just to make sure, I'll provide my steps to reproduce; if nobody else can reproduce it then please ignore me :)
(1) Lock screen
(2) Note that alt+tab doesn't work, and gnome-screensaver's dialog has the focus
(3) Hold down super, and scroll (as if trying to zoom in)
(4) You'll notice gnome-screensaver loses focus and zooming actually works
(5) ALT+F2 and killall gnome-screensaver
After talking to Travis a bit, this is probably a fglrx 8.42 bug.... Just to make sure, I'll provide my steps to reproduce; if nobody else can reproduce it then please ignore me :)
(1) Lock screen
(2) Note that alt+tab doesn't work, and gnome-screensaver's dialog has the focus
(3) Hold down super, and scroll (as if trying to zoom in)
(4) You'll notice gnome-screensaver loses focus and zooming actually works
(5) ALT+F2 and killall gnome-screensaver