When I select preview for an mp3 file, I get DO panel with properties- OK.
But when I select mp3 in a rar or zip archive, I get mp3 layer provided by QuickTime- which is even more strange, because QuickTime is not registered to handle mp3 files (mp3 are associated with another player).
It seems there are two problems here.
This is normal.
The MP3 tag editor plugin doesn't handle files inside zip files (since you'd end up editing a temporary copy of the file and not have your changes saved, among other things).
The ActiveX plugin will also handle MP3 files, assuming you have some kind of ActiveX control registered for the file type (e.g. Windows Media Player or, in your case, Quicktime). At the moment the ActiveX plugin will always handle items inside of zip files. (In the future I plan to make that configurable on a per-filetype basis.)
Aww, OK, case solved. May be worth mentioning in the documentation (ie tag editor not working for files in archives and ActiveX handler use for files in archives).