Comment 3 for bug 693671

Further info...
New Wubi installs only contain two files in /boot/grub: grubenv and grub.cfg

The problem is that when grub.cfg is generated, it fails with syntax errors. The load_video function is empty. This is because the script references a file /boot/grub/video.lst and this does not exist. But with Natty, the syntax errors result in the grub.cfg not being created - instead it spits out an error and leaves the file as grub.cfg.new.

Therefore a fresh wubi install on Natty contains two files in /boot/grub: grubenv and grub.cfg.new. Unfortunately, this makes it impossible to boot wubi unless you boot manually from a command prompt. In addition, running "sudo update-grub" always fails and grub.cfg is never created/replaced.

Note: running grub-install on Wubi to rebuild the wubildr will populate all the grub files into /boot/grub (same as for a normal install), and for Natty (for now anyway) it seems to boot although it spits out syntax errors at startup. However, when grub-install is run on Lucid or Maverick, these errors prevent the installs from booting.

Summary:
New syntax checks for grub-mkconfig fails to create grub.cfg. Therefore new Natty Wubi install does not contain a grub.cfg and cannot be booted.