Since 0.42 release of inkscape I am experiencing crashing with the gtk-qt-engine. All the others gtk applications works fine with the gtk-qt-engine and so does Inkscape except for the Align and Distribute Dialog. Whenever I click on it (new or saved drawing) I get this:
nestorm@...1092...:~$ inkscape QPainter::begin: Cannot paint null pixmap
As you can see from the release notes, this is a known issue which is, however, not in inkscape's reach, as the crash happens in the gtk_qt_engine code. Please file a bug with the maintainers of that package.
Also, it is possible that the problem can be worked around by using another KDE theme than the one you are using now. Some themes are known to crash the system in subtle ways (baghira).
This applies equally for the gtk2-engines-smooth package, and inkscape is not the only application crashing from that theme, as you can see from their SF bug tracker.
Regards, ralf