update-manager popup window not visible

[BeowulfOF]

beowulf@beo-think:~$ lsb_release -rd
Description: Ubuntu 14.10
Release: 14.10
beowulf@beo-think:~$ apt-cache policy update-manager
update-manager:
  Installiert: 1:14.10.6
  Installationskandidat: 1:14.10.6
  Versionstabelle:
 *** 1:14.10.6 0
        500 http://de.archive.ubuntu.com/ubuntu/ utopic/main amd64 Packages
        100 /var/lib/dpkg/status

Update-manager spawns popup with new updates availlable. The Icon for update-manager can be seen in launcher, but the window does not appear, even upon clicking on the icon.
I have to right-click and cancel and then start update-manager manually again to get the window with the new updates.

ProblemType: Bug
DistroRelease: Ubuntu 14.10
Package: update-manager 1:14.10.6
ProcVersionSignature: Ubuntu 3.16.0-24.32-generic 3.16.4
Uname: Linux 3.16.0-24-generic x86_64
ApportVersion: 2.14.7-0ubuntu8
Aptdaemon:

Architecture: amd64
CurrentDesktop: Unity
Date: Fri Oct 31 09:01:36 2014
EcryptfsInUse: Yes
GsettingsChanges:
 b'com.ubuntu.update-manager' b'show-details' b'true'
 b'com.ubuntu.update-manager' b'window-height' b'337'
 b'com.ubuntu.update-manager' b'first-run' b'false'
 b'com.ubuntu.update-manager' b'window-width' b'484'
 b'com.ubuntu.update-manager' b'launch-time' b'1414740971'
InstallationDate: Installed on 2013-10-25 (370 days ago)
InstallationMedia: Ubuntu 13.10 "Saucy Salamander" - Release amd64 (20131016.1)
PackageArchitecture: all
SourcePackage: update-manager
UpgradeStatus: Upgraded to utopic on 2014-10-28 (2 days ago)

[Launchpad Janitor (janitor)]

Status changed to 'Confirmed' because the bug affects multiple users.