I used MP3Tag to put album art into my MP3s and it has never been a problem till now. I loaded a song onto my D2 and the music player won't display the album art when it plays the song. The album art is 400x400 pixels and is named folder.jpg. All my other MP3s have album art that is of similar resolution and is called folder.jpg.
Is there any reason why it wouldn't display it?