The stats that WordPress.com offers roll over at 8:00 EST rather than midnight as one would expect. I have been unable to change that on my wordpress account no matter what I set my timezone to. The post times are accurate but the stats never are, as far as changing at midnight local time.
I also use the wordpress stat plug-in on a self hosted wordpress site and that died like 5 days or so ago. I have no idea why it has stopped recording my self hosted site but is still recording my wordpress site. Just goes to show that wordpress does some good things but they sure ain't Statcounter, by any stretch of the imagination.
It's possible that in the above mentioned situation that text widget is not displayed in the archive section on the theme you have choosen. If that's the case you may be able to fix this by changing to a theme that displays that widget on all pages. It's a sledgehammer fix but unfortunately, when your hosted by wordpress, there arn't a lot of other options.