Comment 184 for bug 192888

Interestingly enough I also had this problem.

But when I installed the http://flashblock.mozdev.org/ extension on firefox, I no longer had the issue. Something to do with not permitting everything to auto load, and allowing me to one by one click flash I wanted to see blocked the issue.

This is not a fix, but a good bandaid for those who want to use it + pulseaudio.