I have KDE 4.14.21 on Slackware 64 14.2. I have the KDE screen locker set to start in 15 minutes and require login after 1 minute [more]. I have the power management settings set to turn off screen after 30 minutes and suspend session after 20 minutes and lock screen.

This all works fine except when I'm running a VirtualBox Windows 7 VM guest. Then the screen saver NEVER kicks in. This is a bit of a security risk, not only in the office, but remote VNC connections are permitted.

A shot-in-the-dark suggestion from the VirtualBox forum suggested there might be some setting in KDE defining how the screen saver works in regards to programs, e.g. playing a video.

Does anyone have any ideas on this?

More info ... If windows are running in the foreground (on top of the guest VM), the screen saver works.