The download directory is now http://www.makemkv.com/download/old/ instead of the currently listed (in .ebuild) http://www.makemkv.com/download/ .
Changelog for package in portage says: *makemkv-1.7.4-r1 (02 Jul 2012) 02 Jul 2012; Matthew Marlowe <mattm@gentoo.org> -makemkv-1.6.16.ebuild, +makemkv-1.7.4-r1.ebuild, +files/makemkv-1.7.4-makefile.linux.patch: Per request from Bug 396253, took over maintainership of media-video/makemkv. Bumped to latest user contributed ebuild. Verified dependencies and installation/operation, supplemented basic elog install directions, and removed obsolete/non functional prior ebuild. So, as ebuild for 1.6.16 was removed, i think this bug should be closed
makemkv 1.7.4 and 1.7.6 are in tree. 1.6.16 has been removed. Is there a specific reason why upgrading to 1.7.x is not the preferred solution?
yeah, use >= 1.7