If there are songs with Unicode in the Artist/Album/Title fields (in the P3 database) the characters will display as ? in the P3 view. The problem (at least on my system) is that is mysql database does not default to utf8. Setting some connection parameters after connecting to the database fixes the problem.
I've supplied a patch (against the current 0.8.8_development master) for a fix (on the Patches page). It works on my system.