There are PHP warnings at the begin of sitemap:
<b>Warning</b>: strtotime() [function.strtotime]: It is not safe to rely on the system’s timezone settings. You are *required* to use the date.timezone setting or the date_default_timezone_set() function. In case you used any of those methods and you are still getting this warning, you most likely misspelled the timezone identifier. We selected ‘America/Chicago’ for ‘CST/-6.0/no DST’ instead in <b>…/wwwroot/function.php</b> on line <b>80</b><br />
You need to fix these warnings. File function.php doesn’t seem as part of WordPress installation. Probably, you need to set timezone in php.ini or set display_errors to Off.
PS: Maybe your website is hacked. Please check content of file function.php.
