Comment 3 for bug 1385930

Same thing happened to me. I just did a test 14.04 install on the same computer so it's not a local issue.

The Fdisk output is odd - looks like it's trying to partition the 6GB root.disk so that it has an efi partition:

Disk /dev/loop0: 1.1 GiB, 1162936320 bytes, 2271360 sectors
Units: sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes
Disklabel type: dos
Disk identifier: 0x4a022e4f

Device Boot Start End Sectors Size Id Type
/dev/loop0p1 * 0 2271359 2271360 1.1G 0 Empty
/dev/loop0p2 2250448 2254991 4544 2.2M ef EFI (FAT-12/16/32)

Disk /dev/loop1: 1 GiB, 1115594752 bytes, 2178896 sectors
Units: sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes
Disk /dev/loop2: 5.6 GiB, 6023020544 bytes, 11763712 sectors
Units: sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes
Disk /dev/sda: 698.7 GiB, 750156374016 bytes, 1465149168 sectors
Units: sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 4096 bytes
I/O size (minimum/optimal): 4096 bytes / 4096 bytes
Disklabel type: dos
Disk identifier: 0x00071c89

Device Boot Start End Sectors Size Id Type
/dev/sda1 * 2048 681983 679936 332M 7 HPFS/NTFS/exFAT
/dev/sda2 681984 177782783 177100800 84.5G 7 HPFS/NTFS/exFAT
/dev/sda4 177784830 1465147391 1287362562 613.9G 5 Extended
/dev/sda5 177784832 960141311 782356480 373.1G 83 Linux
/dev/sda6 960143360 1389404159 429260800 204.7G 7 HPFS/NTFS/exFAT
/dev/sda7 1452785664 1465147391 12361728 5.9G 82 Linux swap / Solaris

Partition 5 does not start on physical sector boundary.