We figured out this problem is caused by the fact that the SB Popular Posts Tabbed Widget is missing the $before_title and $after_title variables from sb-pop-posts-widget.php. Depending on your theme, this can cause problems. In our case, without $before_title and $after_title we ended up missing a closing <div> tag causing any widgets placed below this one to get bumped out of the sidebar.
This modification to the plugin (adding in $before_title and $after_title) fixed the problem for us.
` <?php echo $before_widget;
$title = empty( $instance[‘title’] ) ? ‘ ‘ : apply_filters( ‘widget_title’, $instance[‘title’] );
if ( ! empty( $title ) )
echo $before_title . $title . $after_title;?>
<div class=”sb_tabbed”>
These variables are supposed to be included in all widgets to be compatible with various themes, so hopefully future updates will include this modification! Thanks!