Are you saying that the intro video plays, then there is a drop to black, then it goes to the menu? It could just be your DVD player. There is always a delay when switching video streams. Although on my DVD player the screen just freezes for a second or 2.
You can't do exactly what a commercially produced DVD does with DVD Arch.
What you are talking about is "Delayed Menu Buttons" (which may be coupled with a loop point if you happen to be using a motion menu so that you can get a seemless transition into your menu loop video).
While DVD Arch. does let you specify an intro video, the transition from the video to the menu will never be seemless (and it depends on the player how the transition will be handled; some players will display black, others will simply display the final frame from the intro video).