The SmarterStats software has not been updated recently.
The increased activity maybe due to bots such as Serach Engine Spiders. These would not show up in Google Analytics's as they use JavaScript to collect data and so only show data for browsers with JavaScript enabled.
The SmarterStats software analyses the log files for your website and so can analyses every connection to teh website, not just browsers with JavaScript enabled. You should be able to dig deeper in to SmarterStats to find where this traffic is coming from and see if it bots hitting your site.