freevo-1.7.2 has in RDEPEND: =dev-python/twisted-2.4* but twisted is not SLOTed so we hit an up/down cycle in twisted versions
Does that happens because you've installed something else depending on twisted (and maybe requiring 2.5 or newer)?
Ops, no sorry, this is the freevo dependancy upon twisted-web-0.7 that now has "=dev-python/twisted-2.5*" as a dep. As described at http://bugs.gentoo.org/show_bug.cgi?id=156497#c75 solution is changing freevo dep into "=dev-python/twisted-web-0.6*"
Changed proposed by Matteo, thanks for spotting it, vapier. twisted-web-0.6.0 is also the current stable version. This is going to cause problems in time with things depending on newer twisted(web) versions and the packages going stable. But that issue already has bug #163052, so this one can be closed.