Originally Posted by Marvin the Martian
I have seen it before. It could be one part of the tag is missing. I just found 4 songs on my Clip+ from an album that showed as untagged.....the song titles were missing according to mp3Tag, but rockbox showed the names of the songs because it read the filenames.
So I would suggest connecting to your computer, and opening MP3Tag and accessing the files on the player that show as untagged. Then you should be able too see what's missing and fix it.
I will try this thanks for the idea.