I have some mp3s that I downloaded, so I don't know how they were tagged (dbpoweramp shows the encoder as LAME 3.90a). When I open the files in Mp3tag, it shows that they have only an id3v1 tag. In Winamp, though, I see both an id3v1 and id3v2 tag. The dbpoweramp Windows Explorer extensions also shows both id3v1 and id3v2 tags and claims that the id3v2 tag is id3v2.3 (ANSI). Also, the id3v2.3 tag looks correct when a file is viewed in a binary editor.
This gives problems when trying to edit or convert tags (I need only id3v2.3 ISO-8859-1), since data is often lost by Mp3tag, particularly in long strings and comments.
Attached is a screen shot of one of the files opened in a binary editor. Let me know if you'd like any of mp3 files to figure out what's going on.