Can you manually mount sda6? It could be that the ntfs partition is corrupted, boot into windows, run `chkdsk /r` within the drive where you installed wubi, check that C:\ubuntu\disks\root.disk is still there, and try to reboot into Ubuntu.
Can you manually mount sda6? disks\root. disk is still there, and try to reboot into Ubuntu.
It could be that the ntfs partition is corrupted, boot into windows, run `chkdsk /r` within the drive where you installed wubi, check that C:\ubuntu\