effect: upon world loading, sound doesn't work, and paused amazon streaming video in silverlight in firefox resumes playing (reproducably)

Steps to reproduce:
start an amazon instant streaming video ( http://www.amazon.com/Superman-Cartoons-Max-Fleischer/dp/B00ERQXYZG ),
watch a bit(long enough for the video to start playing) , then pause.

Start minecraft
login (first attempt had to reset password, second attempt didn't... same result)
create new creative world, otherwise stock (not sure if resuming existing world triggers defect)
sound doesn't work, and amazon video (in silverlight/firefox) resumes.

Notes: no media keys are being pressed, minecraft volume and system volume are both up to well-audible levels, other audio sources work outside of minecraft.

3 logs attached in a gzip file. 2 gzipped inside + "latest" log.