No update descriptions available

[Michael Färber]

Since some time, when updated packages are available in Update Manager, it doesn't show release information for a vast majority of packages anymore, just a text that the list of modifications is not available yet. However, even after waiting for some days, this doesn't change.
Clicking the Launchpad link shows the release information, though.
At the moment, I can only see release information for 2 out of 54 updateable packages, which are: libcairo-gobject2 and libcairo2.
I already tried changing the download server from Austria to France, but that didn't fix the problem.

Thanks for looking at this problem. I added a screenshot to illustrate the problem.

ProblemType: Bug
DistroRelease: Ubuntu 12.04
Package: update-manager 1:0.156.14.4
ProcVersionSignature: Ubuntu 3.2.0-24.39-generic-pae 3.2.16
Uname: Linux 3.2.0-24-generic-pae i686
NonfreeKernelModules: fglrx
ApportVersion: 2.0.1-0ubuntu8
Architecture: i386
Date: Sat Jun 9 19:38:23 2012
GsettingsChanges:
 com.ubuntu.update-manager first-run false
 com.ubuntu.update-manager launch-time 1339263460
 com.ubuntu.update-manager show-details true
 com.ubuntu.update-manager window-height 718
 com.ubuntu.update-manager window-width 840
InstallationMedia: Xubuntu 12.04 LTS "Precise Pangolin" - Release i386 (20120423)
PackageArchitecture: all
SourcePackage: update-manager
UpgradeStatus: No upgrade log present (probably fresh install)