Stenno its nothing to be concerned about. It has no effect on a sites level of traffic. I have one site that went from 50 google serps visitors per day to 1000 google serps visitors per day since the last update and there are many internal pages with higher rankings than the home page.
Take Matt Cutts the google engineers site, his homepage is PR5:
http://www.mattcutts.com/
His blog index page is PR 7
http://www.mattcutts.com/blog/
His July 2005 Archives are PR6 (higher than the homepage)
http://www.mattcutts.com/blog/2005/07/
Page Rank is determined for each specific page thats why its called Page Rank and not Site Rank.