Kadu 0.12.2 and earlier is unusable in some configurations with Qt 4.8.3. If one disables Show Offline Buddies option in Kadu, it triggers QTBUG-27122, which is a regression in Qt 4.8.3, and crashes either immediately after start or after clicking at the contacts list. This is worked around in Kadu 0.12.3, which has been just released. You might instead want to revert the offending change in qt-gui or apply upstream fix (not yet in Git at the time of writing: https://codereview.qt-project.org/34877) as other applications might suffer from this. I don't know of any, though. CC'ing the Qt team.
+ 15 Sep 2012; Agostino Sarubbo <ago@gentoo.org> +kadu-0.12.3.ebuild, + kadu-0.12.0.ebuild: + Version bump to 0.12.3, fix qt-gui version for <0.12.3, wrt to bug #435090 Thanks for the report.