Can you please verify that monster-masher requires =dev-cpp/libglademm-2.4* explicitly and will not function with || ( =dev-cpp/libglademm-2.4* =dev-cpp/libglademm-2.6* ) as they are both in the same slot.
Also, you could just stabilize 1.8 as that has been in portage for quite some time.
games-arcade/monster-masher-1.7: depset depends: nonexistant atoms [ =dev-cpp/gconfmm-2.6*, =dev-cpp/gtkmm-2.4* ]
Restored the invalid prunes.
fixed.