Hi. It looks like you may be running into the issue listed in point one of
this thread, for which a full solution is currently not available. Perhaps the 'undefined offset' error is related to CGI timeout. One suggestion is to delete the site from the admin panel, empty the tables, and set LIMIT_DAYS to zero in the config.php file and then crawl on a per page basis where search depth is zero (available since version 1.6.5) or one. Also, if interested see
this thread about the LIMIT_DAYS constant.