Ok, sorry. The error message reveals a problem with the graphical front-end for the GNOME package installer, so let's try from a terminal by now. Be sure the system is connected to internet, open a terminal and login as root using:
Please note the # sign is only the command prompt (you don't have to type it). After that you will use zypper
to download and manage the required packages. First check the installed kernel packages and the available ones:
# zypper search -s --match-exact 'kernel-default*'
this will give you a list of all the kernel-default packages (most likely you will see multiple versions, but only one kernel-default package is installed - check the i in the first column). If it correctly lists also kernel-default-base and kernel-default-devel matching exactly the version of the installed kernel, you can proceed to installation:
# zypper install kernel-default-base kernel-default-devel
zypper will automatically select the correct version, matching the running kernel. If in doubt answer "no" when prompted for confirmation and post the output of both commands here (please use CODE tags for doing so - in advanced mode you have to select the text and click the # button - you will see the text embedded in [CODE]some text[/CODE]).
Hope this helps.