a: I had a similar issue on my Sandisk player and it was due to corrupt data on the SD. Formatting it then copying back the files from a backup solved the problem. the author's problem is different though; it seems his player doesn't like some files although they appear to be undamaged. I agree it's probably a bug in the decoder.
b: a voltage divider would attenuate everything so the listener would end up raising the volume and the noise explosions would be unaffected. In my experience those noises are much louder than the music even at its louder peak, so a limiter would work better. A limiter is a circuit which let the audio signal unaffected up to a given level, then if necessary it starts limiting it to keep it to maximum that level. The limiter should be set up to trigger only with levels above the maximum original audio signal, so that although the noises wouldn't disappear, they would be confined to a lower level with the original signal left untouched.
Ah, I missed the hissing part. Apparently he gets that noise only from a CD player, and that noise is constant through all song and unaffected by volume settings. That would mean the audio section of that player is really noisy and/or possibly the volume control has been put in the wrong place, for example too far (circuit wise, not distance) from the power amplifier section.
When connecting multiple stages together care must be taken to minimize noise. Besides careful design and choosing low noise parts, some practices can at least reduce the perceived noise even on noisy devices, for example by putting the volume control just before the power amplifier. This ensures that when the user lowers the volume the noise generated by previous stages gets also lowered along the signal.
b: a voltage divider would attenuate everything so the listener would end up raising the volume and the noise explosions would be unaffected. In my experience those noises are much louder than the music even at its louder peak, so a limiter would work better. A limiter is a circuit which let the audio signal unaffected up to a given level, then if necessary it starts limiting it to keep it to maximum that level. The limiter should be set up to trigger only with levels above the maximum original audio signal, so that although the noises wouldn't disappear, they would be confined to a lower level with the original signal left untouched.