Ubuntu doesn't lock the screen after suspending when a window-menu is opened

[samvimes]

When I suspend my Laptop (Ideapad U410) by closing the lid, while a menu is open (e.g. through the click on an indicator in the menubar), the desktop is not locked, as it should be. The desktop is locked, when no menu is open.

Ubuntu 12.10
gnome-power-manager version: 3.6.0-0ubuntu1

ProblemType: Bug
DistroRelease: Ubuntu 12.10
Package: gnome-power-manager 3.6.0-0ubuntu1
ProcVersionSignature: Ubuntu 3.5.0-27.46-generic 3.5.7.7
Uname: Linux 3.5.0-27-generic x86_64
NonfreeKernelModules: wl
ApportVersion: 2.6.1-0ubuntu10
Architecture: amd64
Date: Wed Apr 17 15:30:24 2013
InstallationDate: Installed on 2013-01-29 (77 days ago)
InstallationMedia: Ubuntu 12.10 "Quantal Quetzal" - Release amd64 (20121017.5)
MarkForUpload: True
ProcEnviron:
 TERM=xterm
 PATH=(custom, no user)
 XDG_RUNTIME_DIR=<set>
 LANG=de_DE.UTF-8
 SHELL=/bin/bash
SourcePackage: gnome-power-manager
UpgradeStatus: No upgrade log present (probably fresh install)