Comment 49 for bug 477104

Adding bug #477169 as a duplicate, because it is. That's exactly what happened to my first install if initrd is updated. If the kernel is updated, it's "invalid magic number". In fact it looks like any file which is updated from the original stock install reads as garbage from within grub2. For example, after update, grub.cfg reads as garbage, so does /etc/passwd, if accounts were added/passwords changed. If /etc/hosts or /etc/group, just as examples, were never edited, they can be read with "cat" just fine within grub2. I seriously suspect grub2's ext4 support is broken. These files, of course, are perfectly fine, if you boot a live install media of ubuntu and mount the root.disk over loopback. It's only grub2 which has the problem, compounded by wubi's choice of ext4 for the root.disk file.

I'm running 32-bit Ubuntu 9.10, by the way. not 64-bit. So the problem seems to affect everyone equally.