In many Linux (Ubuntu / MINT) distros the flash plugin inisits on running several times the normal speed, making videos impossible to understand. The problem has been suggested to be due to auido ro such. HOWEVER the fix that worked for me was
apt-get install adobe-flashplugin
This installed the adobe version and removed the Ubuntu version. Hope this helps!
10/15 I had another audio problem — audio quit working — at my office. The fix was to uninstall and reinstall PulseAudio and reboot.