Slackware :: Screensaver Password Not Being Asked For

Slackware64, 13.1, Xfce: Sreensaver is configured to Lock Screen After 5 minutes. This works fine. My problem is that 90% of the time, when I go to wake the screensaver, it won't ask for a password and won't come out of screensaver. The only reliable method I have for getting the password prompt is to switch to a console and then switch back to the X session. Then, the screen saver doesn't display, it just asks for a password.

If I move the mouse when the screensaver is active, the screensaver animation freezes for ~20s and then resumes. If I touch a key (Esc, Shift, space, Enter), the animation freezes for ~30s and then resumes. I never see the Enter Password dialog. Screensaver is configured for Random. I haven't reliably gotten it to work often enough to offer any info as to when it works, but it has worked a couple of times. Keyboard and mouse are configured properly (HAL reports "Logitech Logitech USB Keyboard" for my Logitech Elite keyboard and X uses xkbrules evdev; the mouse is an MX Laser, identified as "Macintosh mouse button emulation").