Warning: strpos() [function.strpos]: Empty delimiter in /home/tutuolog/public_html/wp-includes/user.

anyone have a resolve for this warning? It appears 8 times after I log in to admin:

Warning: strpos() [function.strpos]: Empty delimiter in /home/tutuolog/public_html/wp-includes/user.php on line 699

Warning: strpos() [function.strpos]: Empty delimiter in /home/tutuolog/public_html/wp-includes/user.php on line 699

Warning: strpos() [function.strpos]: Empty delimiter in /home/tutuolog/public_html/wp-includes/user.php on line 699

Warning: strpos() [function.strpos]: Empty delimiter in /home/tutuolog/public_html/wp-includes/user.php on line 699

Warning: strpos() [function.strpos]: Empty delimiter in /home/tutuolog/public_html/wp-includes/user.php on line 699

Warning: strpos() [function.strpos]: Empty delimiter in /home/tutuolog/public_html/wp-includes/user.php on line 699

Warning: strpos() [function.strpos]: Empty delimiter in /home/tutuolog/public_html/wp-includes/user.php on line 699

Warning: strpos() [function.strpos]: Empty delimiter in /home/tutuolog/public_html/wp-includes/user.php on line 699

Warning: Cannot modify header information - headers already sent by (output started at /home/tutuolog/public_html/wp-includes/user.php:699) in /home/tutuolog/public_html/wp-includes/pluggable.php on line 866