!!! Multiple package instances within a single package slot have been pulled !!! into the dependency graph, resulting in a slot conflict: app-text/djvu:0 ('ebuild', '/', 'app-text/djvu-3.5.21_p20090103', 'merge') pulled in by app-text/djvu required by ('installed', '/', 'kde-base/okular-4.2.66', 'nomerge') app-text/djvu required by ('installed', '/', 'app-text/ghostscript-gpl-8.64-r1', 'nomerge') ('installed', '/', 'app-text/djvu-3.5.21_p20090103', 'nomerge') pulled in by app-text/djvu[threads] required by ('installed', '/', 'media-gfx/imagemagick-6.4.9.2', 'nomerge') (and 2 more) Explanation: New USE for 'app-text/djvu:0' are incorrectly set. In order to solve this, adjust USE to satisfy 'app-text/djvu[threads]'.
Fixed that when I ran into it. Should be coming your way if you emerge --sync in a bit.