As I already mentioned on #1245468 I could not verify that changing GTK_MODULES, UBUNTU_MENUPROXY, or GTK_IM_MODULE helps in any way.
However, I could verify that the problem GOES AWAYS IN KUBUNTU/KDE when doing:
System Settings -> Application Themes -> GTK -> Choose GTK2 Theme
Choose 'Radiance' instead of 'oxygen-gtk'
As I already mentioned on #1245468 I could not verify that changing GTK_MODULES, UBUNTU_MENUPROXY, or GTK_IM_MODULE helps in any way.
However, I could verify that the problem GOES AWAYS IN KUBUNTU/KDE when doing:
System Settings -> Application Themes -> GTK -> Choose GTK2 Theme
Choose 'Radiance' instead of 'oxygen-gtk'