I go into Slide Show, turn on auto, select 5 seconds, start presentation, slide never changes until I hit arrow keys.
That item does something else than you think: it is for repeating the entire presentation (i.e., it jumps back to the first slide from the dummy last slide, instead of quitting). What you want is to set transition time for all slides: select the "Slide Transition" pane in the right panel and change "Advance slide" to "Automatically after".