2.6. I tried to apply the LIDS patch to kernel version 2.x.x-x that is shipped with my distro and I received errors. What's wrong?

LIDS is developed using the "vanilla" kernel as developed by Linus. Many distributions,including Red Hat, Debian, and Suse, customize their kernels. There is nothing wrong with this, but you should be aware that their kernels are not the same as Linus' kernel. If you want to apply it to a non-Linus kernel, you're on your own. (Debian users, see above notice)