Repository problem after installing kernel-devel

Hi,
I have a fresh installation of OpenSuse 12.3 (with KDE) as guest in a VirtualBox 4.2.12 (Windows 8 host). Everything is 64bit.
After the installation the system has been updated via the regular updater to the latest and greatest.
I get a notification from the system that the guest additions that come with OpenSuse are only of version 4.2.6 and it recommends the update to 4.2.12.
Building the guest additions requires dev-stuff, so I started installing the kernel-desktop-devel package. Some depending packages are installed automatically.
After doing so, there seams to be something fishy with the repository. All related services (apper, zypper, yast, packagekitd) are somehow broken. For example a simple “zypper search kernel” prints “reading installed packages” consumes 50% CPU and does not return.
This is fully reproducible on my machine (I reinstalled OpenSuse four times), but I’m not sure if this caused by Virtual Box or anything else.
Any idea would be appreciated.
Regards
Michael

In the meantime I reinstalled the system, again. This time I kept the 4.2.6 Guest Additions and went on installing the other stuff that I need. Later I tried to install the kernel-devel stuff again and this time it was no problem at all. :\