The ID3 tags of the MP3s are in Chinese or something. CDex is set to English. This occurs in CDex 1.79 and 1.80, but not in portable 1.77.
There is another version on the official website that has been released a few days ago. Try installing that one and then check the behavior. Alternatively, you can manually modify those field to match the data you need, but if this still happens, then I recommend forwarding this issue to the official developers.
Also check the FAQ page for additional fixes to common errors: http://cdex.mu/faq
I have the same problem with the last versions, all ID3-tags are written in chinese or other asian letters, does anyone knows a solution?