This Plugin is loading quite a lot of scripts:
wp_enqueue_script( 'jquery' );
wp_enqueue_script( 'jquery-form' );
wp_enqueue_script( 'date', "https://wordpress.stackexchange.com/" . PLUGINDIR . "https://wordpress.stackexchange.com/" . $plugin_dir . '/js/date.js', array('jquery') );
wp_enqueue_script( 'bgiframe', "https://wordpress.stackexchange.com/" . PLUGINDIR . "https://wordpress.stackexchange.com/" . $plugin_dir . '/js/jquery.bgiframe.js', array('jquery') ) ;
wp_enqueue_script( 'datePicker', "https://wordpress.stackexchange.com/" . PLUGINDIR . "https://wordpress.stackexchange.com/" . $plugin_dir . '/js/jquery.datePicker.js', array('jquery') );
wp_enqueue_script( 'textarearesizer', "https://wordpress.stackexchange.com/" . PLUGINDIR . "https://wordpress.stackexchange.com/" . $plugin_dir . '/js/jquery.textarearesizer.js', array('jquery') );
if( strstr($_SERVER['REQUEST_URI'], 'wp-admin/post-new.php') || strstr($_SERVER['REQUEST_URI'], 'wp-admin/post.php') || strstr($_SERVER['REQUEST_URI'], 'wp-admin/page-new.php') || strstr($_SERVER['REQUEST_URI'], 'wp-admin/page.php') || $post->post_type=='page' ) :
wp_enqueue_script( 'editor' );
endif;
It’s possible that there’s a conflict.
Are you sure the issue began with WordPress 3.1.1, rather than with 3.1? The jQuery version in 3.1 was bumped up; I’m unaware of any script version changes in 3.1.1, but I could be wrong.