After a fresh install of openSUSE 12.3 with KDE 4.10.4 from the upstream repos (see: https://en.opensuse.org/KDE_repositories#Upstream_release_aka.KR410.28KDE_SC_4.10.29) I didn’t changed the default settings of the auto-screen lock after 4 minutes without a screensaver.
Now, when the screen gets auto-locked (e.g. a screensave would start), I see the unlock window/widget for entering my password. However, after moving the mouse just a little bit, the screen gets unlocked without entering anything.
Nevertheless, I discovered that when specifying a time (in seconds) of 1 after which a password is requested (*), the above behaviour is worked around.
I’m not quite sure whether this is a openSUSE specific or KDE upstream problem. Or whether it’s a bug or a feature.
that’s the second option in Systemsettings -> Hardware -> Display -> Screen Lock
The issue is mainly cosmetic though, it’s just that the screen locker shows the password request screen even when not requesting a password (can be misleading of course, you could think your system is locked when it isn’t).