I can confirm this bug, and provide some output. This is on Kubuntu 9.04 development branch up-to-date as of 14:00 CET today.
$ dbus-send --print-reply --type=method_call --dest=org.freedesktop.ScreenSaver /ScreenSaver org.freedesktop.ScreenSaver.SetActive boolean:true method return sender=:1.24 -> dest=:1.115 reply_serial=2 boolean false
$ dbus-send --print-reply --type=method_call --dest=org.freedesktop.ScreenSaver /ScreenSaver org.freedesktop.ScreenSaver.SimulateUserActivity method return sender=:1.24 -> dest=:1.116 reply_serial=2
I can confirm this bug, and provide some output. This is on Kubuntu 9.04 development branch up-to-date as of 14:00 CET today.
$ dbus-send --print-reply --type=method_call --dest= org.freedesktop .ScreenSaver /ScreenSaver org.freedesktop .ScreenSaver. SetActive boolean:true
method return sender=:1.24 -> dest=:1.115 reply_serial=2
boolean false
$ dbus-send --print-reply --type=method_call --dest= org.freedesktop .ScreenSaver /ScreenSaver org.freedesktop .ScreenSaver. SimulateUserAct ivity
method return sender=:1.24 -> dest=:1.116 reply_serial=2