Comment 2 for bug 441941

To reinstall GRUB 2 from a Live cd see this guide: http://grub.enbug.org/Grub2LiveCdInstallGuide

Seems like something in your Windows is overwriting the embeding area.
The only workaround for this, which isn't recommended, would be to install GRUB 2 to a bootsector and use some MBR code which doestn't use the embed area, like Microsoft's or the one from the mbr package.
In that case the partition with the GRUB 2 bootsector needs the boot/active flag.