You can download the updated version here:
Post Levels 1.1.2
If you are curious, the problem was due to a regular expression that was not expecting the SQL "FROM" clause to use an alias for the "wp_posts" table. My solution, which is a bit hacky, was to insert expressions to create and then properly handle this alias. I wish a better solution exists, but to my knowledge WordPress doesn't expose these SQL statements through hooks.
Please let me know if you have any issues.