It turns out that I messed up the code in MetaSync that checks whether you’re running MediaPro 2.X or MediaPro 3.x (as the Applescript dictionary is different in 3.X). If you’re running a newer 3.1.X version of MediaPro, it’s likely that you’ll find that the Ratings field over the MetaSync panel is greyed out (as MetaSync thinks you’re really running MediaPro 2.X).
I’ve just tweaked the code that does the version check and released MetaSync 1.5.3 to fix this problem. You can download it from the usual Software page.
And, yes, I’m still planning to release MetaSync 2.X at some point. Unfortunately, I’ve got a few other coding projects ahead of it on the list that need to be completed first. 🙂