I know its an old thread, but I had the same problem and I found the reason for this. I created the VM and selected for USB Bus, VirtIO Bus and vDisk Bus the Option "SATA" as I know it is faster than IDE. But using "SATA" is wrong for the vDisk Bus. After booting with this setting it displays the driver as meph88 mentioned, but its not possible to install it. Editing the VM and changing it back to "VirtIO" does not help. Instead it is needed to set a new vDisk path, which creates a new disk image or to delete the VM including the vDisk and create a new VM. This explains why it worked for meph88 with the different ISO I think (as he then used the default settings I think).