As far as I can tell, I believe I unknowingly and gradually damaged it over time through static discharge. I think the headphones being wrapped around it while plugged in meant that rubbing against clothes (especially in winter when I wear a scarf and a thick winter coat, and cold means low resistance) would send a current down the cable. The fact that the outside casing is also made of metal (why the heck?) also hasn't helped - I'd frequently get shocked by it during dry winter days. Oh well, I think I'll make the switch to my phone as my mp3 player now, it's just a shame because I liked the equalizer on the Sony a lot, not to mention it being smaller and cheaper than my phone.
Your 64gb model might survive a format of its data partition - my S544 got stuck on building its library twice I believe, and both times I formatted it to get rid of whatever corrupt data was on there. It's pretty incredible how easily these things break.