Thanks, Jim.
I had originally had MJ8 in a directory called D:\Program Files\Media Jukebox\
I then uninstalled MJ8 but did not delete that directory, and installed MC9 in D:\Program Files\Media Jukebox 9\
When I uninstalled MC9, I also deleted the MC9 directory, and all the registry entries.
I then installed MJ8 in a directory called D:\Program Files\Media Jukebox 8\ (note it's different than the previous MJ8 install) This was giving me the trouble I posted earlier about.
At your suggestion, I uninstalled MJ8, removed the registry entries, and deleted both MJ8 directories (D:\Program Files\Media Jukebox\ and D:\Program Files\Media Jukebox 8\)
Did a reinstall of MJ8, and voila! It imported my MP3s!
Kinda strange, though how the 2 directories interacted? I wasn't expecting that, and that's why I didn't bother to delete the original directory.
-Mr.X