Comment 12 for bug 1287255

The most recent version of light-locker, 1.4.0, was recently uploaded to Trusty and it addresses the issue of not being able to deactivate light-locker on suspending. This is also reflected in light-locker-settings, where you'll find a new switch to disable this behavior.

Note: currently the options in xfpm, xfce4-session and light-locker-settings aren't yet in sync (there's a separate bugreport for that), but we're working on it. Anyhow, this bug – as reported – is fixed.