I'm running KDE 4.14.21 on Slackware64 14.2 and VirtualBox 5.1.6. I have the KDE screen saver (System Settings > Display and Monitor > Screen Lock) set to start after 15 minutes and require login after (another) 60 seconds. Normally, this works fine. However, when I am running VirtualBox with a WIN7 guest OS the screen saver never kicks in. UNLESS, I have something else running in the foreground (on top of the VM). I've tried this with Konsole and Firefox. If these are running in front of the VM the screen saver works. If VirtualBox is running in the foreground the screen saver never works. This is a bit of a security issue as the user must either close the VM, or put something on top of it if leaving the workstation unattended. Even a bigger problem if accessing the workstations remotely via VNC.

Also, if the VM is minimized the screen saver works.

Any ideas?