Can also confirm this bug, or something similar is present in the latest 15.10 ISO downloaded from http://www.ubuntu.com/download/alternative-downloads (torrent) as of 3/10/2016. I'm installing within a Gen 2 Hyper-V machine to a completely blank vhdx. Tried to create 3 partitions for EFI boot, root / in btrfs, and a swap. Got the error exactly as described. Also experienced a couple crashes before that to even get that far!
Can also confirm this bug, or something similar is present in the latest 15.10 ISO downloaded from http:// www.ubuntu. com/download/ alternative- downloads (torrent) as of 3/10/2016. I'm installing within a Gen 2 Hyper-V machine to a completely blank vhdx. Tried to create 3 partitions for EFI boot, root / in btrfs, and a swap. Got the error exactly as described. Also experienced a couple crashes before that to even get that far!