Yup. I have successfully built a pure 64-bit CLFS on an AMD64 platform. I followed the instructions in the CLFS book for the pure 64-bit build. After completing the base system build, I built Xorg and GNOME and many other packages. Something went wrong with your build if that is the problem you're getting.
The commands for building several of the packages in the toolchain and elsewhere are different for a 64-bit build (CLFS) than they are for a 32-bit build (LFS). You might get a stable 64-bit build using LFS and adjusting the commands therein appropriately, but you're better off using CLFS.
Also bear in mind, the x86_64 ABI is considered a multilib architecture. The pure 64-bit CLFS book doesn't treat it that way (see this mailing list post
http://lists.cross-lfs.org/pipermail...h/000587.html). The CLFS gcc-pure-64 patch undoes what is *correct* according to the standards in the gcc code. The pure-64 CLFS is not standards compliant whereas the multilib CLFS is. You really should use the multilib book for an x86_64 architecture.