First of all, good plugin, just what I needed!
I just upgraded from plugin version 1.0.6 to 1.0.7 and first thing I did was browsing in the back-end to Media Categories and click in the Sort column on Sort Media Items like you suggested in the readme. When clicking that link I've got the following php error.
Fatal error: Call to undefined function cleanQuery() in .../wp-content/plugins/media-library-categories/sort.php on line 42
When I find the time, I will look into this myself, but just wanted to notify you.