Shucks! (I'll bet you said something similiar). I guess it's safe to assume the problem is not limited to downloaded songs only. Therefore, must be the player. You need to supply us with a little more info:
What's your operating system and what player do you use?
When did problem begin?
What have you done to troubleshoot?, i.e., played a cd, tried different player (if your using LW's player, then that's ur problem).
I'm sure someone here can help.