Created attachment 9653 proposed solution After some recent update xfce4-power-manager started to show a message which says: "None of the screen lock tools ran successfully, the screen will not be locked.\nDo you still want to continue to suspend the system?" which prevents machine from going to sleep. Closed lid also produces a similar message: "None of the screen lock tools ran successfully, the screen will not be locked." As I was digging, I found that xfce4-power-manager makes a synchronous D-Bus method call, but handlers in xfce4-screensaver never send a reply to "Lock" method call. I guess the right solution is to add an empty reply to the xfce4-screensaver. Patch attached. Also, there was a minor issue with message filtering which resulted in handling all paths, not only "/org/xfce/ScreenSaver", as were designed. Last two hunks in the patch are related to that minor issue.
this were resolved in the latest master
(In reply to Alexander Butenko from comment #1) > this were resolved in the latest master Thanks. It's fixed indeed. Will mark this as a DUPLICATE then. Also, I found that recently released xfce4-screensaver-0.1.10 also has the issue fixed. *** This bug has been marked as a duplicate of bug 16522 ***