Comment 21 for bug 226470

My guess is that what happens is a subframe's window gets created as a top level widget by mistake. (The crash occurs later so a stack might not help.) I really have no idea how that could happen. A mess of logging code in nsWindow::NativeCreate might help; maybe run under gdb for a while and use a breakpoint with commands to dump a detailed stack every time a top-level GTK window is created ?