This is the MySQL 5.0.50/51 bug. Looks like your host just upgraded their MySQL version. Unfortunately a lot of hosts are upgrading MySQL now, and they’re all doing it to these buggy versions. WordPress is doing the right thing, their version of MySQL is not.
Find this in wp-includes/post.php (around line 260): $query .= " GROUP BY $wpdb->posts.ID ORDER BY " . $orderby . ' ' . $order;
Change it to this: $query .= " ORDER BY $orderby $order";
That should solve it. But this is a temporary fix only, some other types of get_posts calls won’t work with this fix.