I noticed this yesterday.
After about 15 minutes on inactivity, I have my laptop screen set to lock so I can comply with my company’s security policy. In the past, a unlock dialogue would appear, but now the screen locks and I see the wallpaper, but no unlock dialogue appears. If I manually lock the screen with a keyboard sequence I get the dialogue.
I am running Tumbleweed with Kernel 3.12.7-7, KDE 4.11.4