Two warning messages

Love the Plug-in but suddenly I am getting
Warning: extract() [function.extract]: First argument should be an array in/homepages/40/d275914903/htdocs/wp-includes/pluggable.php on line 216
after users submit their email address for confirmation. Tried reinstalling but didn’t help. Any ideas.
Brian

http://ww.wp.xz.cn/extend/plugins/participants-database/