Portage wants to upgrade madplay 0.15.2b, then on next emerge -uD world downgrade it to 0.15.1b. This repeats indefinitely. Portage tries to downgrade madplay because the meta-package media-sound/mad lists specific versions for packages. Maybe it makes more sense to change all the "~"s in mad's DEPEND to ">="s.
ok... that's it... that metapackage is getting the boot... it's not needed.
mad metapackage was removed from portage ... madplay emerged depended on everything in that metapackage, so there is no need for it.