What gives? This handy page
is always hidden deep in Google search results for me but it (really Missinglinq
gets the credit) explains what is happening. Apparently Access reserves space at the bottom of the form for navigation buttons and (horizontal) scroll bars. If you need the scroll bars they'll pop up, if you don't well, I guess they are hidden behind the navigation buttons. If you hide the navigation buttons you reveal the hiding scroll bars.
The trick is to disable Horizontal Scroll bars, too. You can either set the Scroll Bars to Neither or Vertical only. Both disable the horizontal component.
Set Scroll bars to Neither