I had what sounds like a very similar problem yesterday. I was listening to music over the HTC 8X's speaker and it would randomly sound VERY distorted. As if the speakers were blown, but it was completely random (it didn't necessarily occur when lots of bass or treble were in the song). It was distorted probably about 50% of the time, but again, it was totally random when it would decide to distort. I put up with this for about an hour before finally shutting it off. A few hours later my phone decided to reboot itself, and I tried listening to music again and it worked just fine after that. I also had the Lumia 710 before and it was bullet proof! Never rebooted itself a single time and the speakers were pretty decent.