I have seen similar issues earlier when Gtk-apps did not play nicely with the Desktopmanager theme (not the iceweasel themes). Could you try to change:
- your KDE theme (for example from oxygen to something else, try iceweasel, change back)
- your Gtk-setting in KDE's systemsettings (gtk2 and gtk3 themes, from Clearlooks or Adwaita to sth else, try iceweasel, and back to Adwaita)
For Adwaita/Clearlooks to integrate well in KDE you need the package gnome-themes-standard (if I remember that right).