Google Sitemap Problem

Warning: mktime() expects parameter 1 to be long, string given in /home/dtemple/public_html/test/wp-content/plugins/google-sitemap-generator/sitemap.php on line 2655

Warning: Cannot modify header information – headers already sent by (output started at /home/dtemple/public_html/test/wp-content/plugins/google-sitemap-generator/sitemap.php:2655) in /home/dtemple/public_html/test/wp-includes/pluggable.php on line 865