SANDISK mp3 player problems

Hello, I had purchased a Sandisk mp3 player 250 for Xmas for my daughter and I was able to plug it up using the usb port. Everything was fine at first it recognized it and I was able to download music from itunes onto the player and everything worked fine. I recently purchased me one the same kind and it will not recognize it AT ALL!. Not for sure why. Is there anyway I can get my ibook g4 to recognize the folder where it shows the mp3 attached. I know the USB is working because when i plug it up it is charging. I tried to download Windows Media 9 for mac to download music to it but i can not successfull open the file. I was able to download a cd onto the player at work because it is an XP not for sure why the first time i was able to download the songs first time and now i dont see it. I have a ibook g4 by the way. Please help desperately wanting to listen to songs on mp3 player. I should have got a nano but this Sandisk offers a lot more for the price.