grub "can't install in /dev/sda" - 12.10

[diegobalangione]

I cant install the grub in the instalation,
the installer show my a mensage of this error, and give my 4 option:
/dev/sda
/dev/sda3
/dev/sda4
/dev/sda6

but nothing work :-(

-------
ubuntu@ubuntu:~$ sudo fdisk -l

Disk /dev/sda: 320.1 GB, 320072933376 bytes
255 heads, 63 sectors/track, 38913 cylinders, total 625142448 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 identifier: 0x000e489e

   Device Boot Start End Blocks Id System
/dev/sda1 2046 470894591 235446273 5 Extended
/dev/sda3 * 470894592 471099391 102400 7 HPFS/NTFS/exFAT
/dev/sda4 471099392 625139711 77020160 7 HPFS/NTFS/exFAT
/dev/sda5 449220608 470894591 10836992 82 Linux swap / Solaris
/dev/sda6 2048 449220607 224609280 83 Linux
---------

ProblemType: Bug
DistroRelease: Ubuntu 12.10
Package: ubiquity 2.12.0
ProcVersionSignature: Ubuntu 3.5.0-15.22-generic 3.5.4
Uname: Linux 3.5.0-15-generic x86_64
ApportVersion: 2.5.2-0ubuntu4
Architecture: amd64
CasperVersion: 1.324
Date: Thu Sep 20 22:02:05 2012
InstallCmdLine: noprompt cdrom-detect/try-usb=true file=/cdrom/preseed/ubuntu.seed boot=casper initrd=/casper/initrd.lz quiet splash -- maybe-ubiquity
LiveMediaBuild: Ubuntu 12.10 "Quantal Quetzal" - Alpha amd64 (20120920)
ProcEnviron:
 LANGUAGE=es_AR.UTF-8
 TERM=unknown
 PATH=(custom, no user)
 LANG=es_AR.UTF-8
 SHELL=/bin/bash
SourcePackage: grub-installer
UpgradeStatus: No upgrade log present (probably fresh install)

[Launchpad Janitor (janitor)]

Status changed to 'Confirmed' because the bug affects multiple users.

[solax (solax76)]

This bug affect also me, I had a similar disk partition with dual boot and after installing Ubuntu 12.10 I had no issue in executing Ubuntu, but I was completely unable to start my Win7 system.
I though was an error on MBR an I have taken this opportunity to format the disk completely, so I have reinstalled again Ubuntu making a new partition table:
1 Primary ext4 with mount point /
1 Primary ext4 with mount point /home
1 Extended with logical Swap
1 Extended FAT32 (with HP tools on my HP dv6 laptop)

At the end of installation process I had the "can't install in /dev/sda" error message, and rebooting the system, grub was unable to find the boot disk.
I tried different times also changing the home partition with and Extended ext4, but with the same result.
I have also tried with the Ubuntu Boot-Repair tool and other guides on the web to recover grub installation, but without success.

Now I have installed Ubuntu 12.04 without any issue.
Hope this will help to solve the problem.