The way WordPress runs some mysql queries has changed in 3.9 and mysql_query is deprecated in favor of mysqli.
Replace these two spots in wp_clean_up_admin.php:
line 108
function wp_clean_up_optimize(){
global $wpdb;
$wcu_sql = 'SHOW TABLE STATUS FROM '.DB_NAME;
$result = $wpdb->get_results($wcu_sql);
foreach($result as $row) {
$wcu_sql = 'OPTIMIZE TABLE '.$row->Name;
$wpdb->query($wcu_sql);
}
}
line 363
global $wpdb;
$total_size = 0;
$alternate = " class='alternate'";
$wcu_sql = 'SHOW TABLE STATUS FROM <code>'.DB_NAME.'</code>';
$result = $wpdb->get_results($wcu_sql);
foreach($result as $row) {
$table_size = $row->Data_length + $row->Index_length;
$table_size = $table_size / 1024;
$table_size = sprintf("%0.3f",$table_size);
$every_size = $row->Data_length + $row->Index_length;
$every_size = $every_size / 1024;
$total_size += $every_size;
echo "<tr". $alternate .">
<td class='column-name'>". $row->Name ."</td>
<td class='column-name'>". $table_size ." KB"."</td>
</tr>\n";
$alternate = (empty($alternate)) ? " class='alternate'" : "";
}