http://www.kdenlive.org/ says that kdenlive's config wizard freezes with 0.7.2 and mlt-0.3.4. A week ago they released a bugfix version (0.7.2.1), available through the usual sorceforge download. While I personally also experienced that freeze, it's not a total freeze, it just takes some minutes until the application reacts again ( my machine at least). Renaming the 0.7.2 ebuild worked for me here. See also bug #257966
fixed in tree.