Hi. I've got WinXP and Mp3tag v2.36f (WONDERFUL program, BTW; just upgraded from 2.36a per the note) and was sifting thru my WV, M4A, and MP3 files, and came across an interesting "feature".
Bring up a new explorer window and search for some files. I did *.M4A, but it seems to break with anything; just search for something with a few hits in a few different directories.
Hit ^A (or Edit / Select All), then drag and drop the files to mp3tag and....surprise! You get (only) the files from the directory of the last search result. (Not "All" by any stretch of the imagination. )
Now select just one and drop it, and you'll get all files in that particuar directory. Choose another file from another directory; same thing. It works and all, it's just grabbing files from one single directory only.
I found it since I wanted to check a comment for all M4A files -- once again, tagging and all seems fine, it's just Windows Drag-N-Drop interaction that produces a weird result.
(BTW, I'm using foobar to do high res to low res MP3 transcoding for a portable MP3 player -- it's a neat player / converter, if you've not seen it. And of course EAC for CD ripping, and then a lossless codec (wavpack) for storing.)
Once again, thanks for a very nice tag editor!! (Now if you could just speel check my entires for me... )