I just noted that when using ALLEGRO_FULLSCREEN_WINDOW with OpenGL the display is created slightly offscreen. You can see it with ex_fs_window; the display will be originally offscreen but will be correctly placed after toggling the window mode.

This happens on my machine with Windows XP SP2 and an old integrated Intel card.

This might be related to another bug in al_set_new_window_position() that causes the same kind of displacement with both Direct3D and OpenGL.