Comment 3 for bug 78901

I investingated a bit and it seems that update-manager takes the kernel parameters from fstab (where I have the correct UUIDs) unless kopt options are present in grub configuration's file. And my menu.lst had these two lines:

# kopt=root=UUID=...
# kopt_2_6=root=/dev/hda2

So the last line was used as the kernel root parameter.
I deleted that line and update-grub worked as expected using UUID.

Anyway something must be done to prevent this.