Gtk3 MacOS (OSX) context menu issues

[Konstantin Dmitriev <ksee zelgadis gmail com>]

Hello!

My name is Konstantin Dmitriev, I am a maintainer of Synfig Studio
open-source animation software.

Recently we have ported our software from Gtk2 to Gtk3. Unfortunately,
after that we have encountered issues with context menus on OSX - the
context menus are become insensitive sometimes. This happens randomly,
but quite often.

I have recorded a video to illustrate the problem -
http://www.youtube.com/watch?v=Cscz45WeFEs

I am stuck with this issue and don't know how to solve it. Any help,
hints, suggestions are highly appreciated.

Some information about the build environment:
Gtk version 3.14.8, everything built through MacPorts environment.
Gtk backend type: XQuartz.

I will be happy to provide any additional information.
Thank you!

Konstantin.