Opening a GtkWindow from a Thread

[vbutty12 netscape net]

Dear all, 
 
I am desperatly trying to open a dialog box from a thread on Windows XP. The dialog box is indeed
opening, but when I try to move it from its initial position, the GUI freezes. 
The only way I could find to let the application work is to create the dialog box at the start
of each thread (before calling gtk_main) and then use the gtk_widget_show / hide procedure.
Unfortunately, this method is not really suited to my needs.
 
Does anyone have an idea on how I could stabilize the GUI ?
 
Sincerely,
 
Vincent Butty