I seem to be having the same problem. Sansa fuze 4 gb I downloaded an update for it when I got it a few weeks ago refurbished. 8 gb sandisk micro sd (forgot what class) with two flac albums for testing ran without problems. 32 gb micro sd card class 4 sandisk with my thousands of mp3 and flac and some other file types such as txt and jpg ran slowly when opening music list. Music playback ran slowly and laggy on either file type.