GtkOptionMenu problem after loosing focus

If I have a GtkOptionMenu which I select, which then drops down a list and
then I decide that I dont want something from that list, but instead I want
to click on a button that is on the same window, that button can not be
pressed. This is EVEN though the GtkOptionMenu has been close as a result
of loosing focus.

If I move the mouse off the window and then back on (without clicking) I can
then press the button that I wanted to press; similary, if I click on the
window itself, I can press the button.

Is this a fault with GTK or have I made the mistake somewhere in my code? I
am using Gtk v1.3 for windows (build 20020314).