did you try manually reinstalling the player firmware? Sometimes the firmware in the player becomes corrupted. Don’t insert or remove a card while the player is on. USe Sandisk class 4 cards for maximum compatibility.
Cards faster than class 4 are likely to cause issues. Some other brands of cards might give issues, even if they are class 4 or slower.
http://forums.sandisk.com/t5/Sansa-Fuze/Sansa-Fuze-Firmware-Update-01-02-31-amp-02-03-33/td-p/139175
