I received the following error while trying to access Reports in Silverstripe 2.2.2:

Fatal error: Class 'Report_StatsReport' not found ...

This error is referenced here and here, but the details were lacking.

To fix the problem remove the following comment from /ecommerce/code/reports/Report.php

/*class Report_StatsReport extends Report {

        static $title = "Website statistics";
        static $description = "View statistics of this website";

        static $awstatsURL;
                static function set_awstatsURL($pass) {
                self::$awstatsURL = $pass;
        }

        function getReportField() {
                 
                $awstatsURL = self::$awstatsURL;

                return new LiteralField( 'AWStats', "<iframe name=\"reportframe\" class=\"AWStatsReport\" src=\"$awstatsURL\"></iframe>" );
        }

        function getOwnerID() {
                return $this->class;
        }
}
*/