How to communicate between two gtkmm windows

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Hi Guys,

What is the right way to communicate between 2 gtkmm windows??? 
How should i show the 2 windows? 1 gtk::main() and the 2nd just shown? or two gtk::main() loops?

Problem describtion:

I still having the same problem as I posted before. I have a MainWindow with a simple Toolbar out
of Buttons, sometimes on a Button click i have to change the pix_label. That works fine as long as
that is triggerd by the signal_clicked event of the Button.
Besides my MainWindow I also have a Optionsdialog, If I change some Options in that window I
also have to change some pixlabels of the buttons in the mainwindow, to indicate that something 
changed.
And that thing makes me trouble. I wrote a new little testprogramm, just to play with that thing 
around. No matter how i try to change the button (dispatcher, signal, direct) the button gets thin, so
the pixlabel gets removed but no new one is added.
ok i tried to keep out the pixlabel thing and i did the same thing with just a label, and it was the 
same, the label is removed but no new one is added.

my optionsdialig don't run in an extra mainloop at the moment, its just shown out of the 
mainwindow.

then I tried to put the dialog in a 2nd gtk::main() loop, and then the hole stuff worked fine in the
small testprogramm. I toke my project and change it that way, but now i a get a segvault after
closing my dialog...somewhere in gtkmm.

so whats the right way...???? if you like i can send you my small testprogramm! 

thanks in advance for any hints! 

Alex