Software :: Reformatting Mp3 Using Mac

I have a Sandisk m240 Mp3 player 1GB. I use it almost every day. I have had it since Sept 2008. I have had a few problems with it, but they were small issues that I could overlook. One of those problems is, every time that I put more than 100 songs on my mp3 player (it can hold about 240 depending on size of file), there would always be one song that came up as "unknown". I could play the file, but it would still be "unknown", even when I knew perfectly well that the file was ripped off a cd (that I own) to my computer (which plays it perfectly fine). That problem I was able to overlook because the file would still play.