Comment 16 for bug 1415918

Well, that issue appears to be caused by stale data on the disk, and that's probably something like that pre-existing PReP partitions aren't being handled properly.

Could you try to just manually wipe /dev/sdX1 (replacing X with whatever device you choose to install on), using 'dd if=/dev/zero of=/dev/sdX1', see if just this is sufficient to let the installer complete successfully?

I still don't know why this might be happening, but I've also built a version of grub-installer in my PPA that ignores the failure to wipe a PReP partition and carries on with the installation: https://launchpad.net/~mathieu-tl/+archive/ubuntu/installer-dev/+packages. That package will need to be installed manually before the installer reaches the point where it would install the bootloader.

I'm still waiting to get access to a proper LPAR to do better testing on this, so as soon as that is available I'll update here and do my own testing as well to try and reproduce the issue here.