I use statcounter to keep tabs on my traffic/analytic information, and I've noticed that I get a hit on my blog from the same IP address somewhere between 5am and 7am every morning. However, it isn't always registered as a view with wordpress. It's an IP in town...but of course I don't know much more than that.
could this be someone with an rss or some other 'feed' or 'auto' hit? They're using XP and firefox if that makes any difference.