Since Adobe has introduced Flash, there have always been major and minor problems with that on all platforms, especially on Linux. One problem I often had to deal with is a focus stealing bug with Kwin, KDE's window manager.
Gnome and KDE come more and more together but there are still some differences which sometimes might lead to incompatibilities between these two large desktop environments. Whereas you have relatively few problems with KDE applications on Gnome there are far more problems when using Gnome applications on KDE even though there are some compatibility engines.
In this Howto Blog post I'll show you a way to converge GTK and Qt as much as possible from the perspective of a KDE system.