FocaaBR, so how is it going for you? Based on your other posts it would look like you've went past that problem you mentioned above, is that correct?
lawliet, I've updated my Ubuntu VM up to the latest patches, then built an "image-full" without a hitch, without the modification you've mentioned in your original post. To be honest I'm sort of out of ideas, given we're using the same OS. Are you sure you have all the latest patches and all the prerequisites installed? Let's also maybe take a look at your sed version, which one have you got?