Comment 4 for bug 477169

Is this a grub error or a linux one? I understood it was the latter.
To be more precise I understood that from grub, without any change, you are able to load the Linux kernel and initrd, but the initrd scripts cannot locate the root device.

So I would expect you to end up in a busybox shell within linux (not grub).
In there can you try to mount the windows partition?