Mixxx 1.10 runs fine without the QT3 dependency (x11-libs/qt-qt3support:4), according to upstream the QT3 to QT4 merge is complete: http://www.mixxx.org/wiki/doku.php/code_cleanup https://code.launchpad.net/~mixxxdevelopers/mixxx/qt3-removal I've modified the ebuild, removed the x11-libs/qt-qt3support:4 dependency and successfully compiled and run Mixxx afterwards.
Fixed in CVS.