By looking at https://bugs.launchpad.net/ubuntu/+source/linux/+bug/1079846 I figured out that enabling in Virtualbox>Settings of my Kubuntu virtual machine>System>Processor the "Enable PAE/NX)" setting made installation of the generic kernel succeed.
By looking at https:/ /bugs.launchpad .net/ubuntu/ +source/ linux/+ bug/1079846 I figured out that enabling in Virtualbox>Settings of my Kubuntu virtual machine> System> Processor the "Enable PAE/NX)" setting made installation of the generic kernel succeed.