Actually a filter function called “postlevels_query” in Post Levels is very tricky and buggy, the comment of that function claims that “This is almost guaranteed to break some day”. It does some string replacements for SQL query, which is really dangerous….
Some SQL query strings from Terong use “p” as an alias of the table $wpdb->posts, so the hacks of Post Levels failed…
I changed some codes in Terong Related Links, now it works. You can download it here – Terong Related Posts changed by Wei Wei
This conflict is no one’s fault….en