can’t install Android-x86 in Virtualbox

I encountered a problem with the installation of Android-x86 in VirtualBox. If this topic has already been handled in a different post please give me a link.

Let me give you some details:
my machine: Ubuntu 14.04, VirtualBox 4.3.43, AMD-chip as CPU (if this is of importance)

Android-x86: version 6.0 and version 5.1-rc1

behaviour; I created the virtual machine, added the iso-file as a CD and started the VM. I can see the menu allowing me to choose between Live-CD (3 choices) and installation. Whatever I choose it crashes within a second and the line ‘press F12 to select boot-device’ appears, followed by the initial menu.

Do you need more information?

What am I doing wrong here? Do you have a tip for me?

Thanks
August

PS: I also have an older version here in a VM (Android 1.6r2) which runs fine.