Mozilla just announced a security flaw a couple of days ago. They've got a patch up on their site (addons.mozilla.org). The patch (the page includes directions on how to do it manually) turns off IDN (International Domain Name) functionality, so hopefully you're not going to go to any sites that use non-ASCII characters in their domain names.
You wanted the best, you got... Out of Context Quote of the Week.
"...but that doesn't mean he can't relate an amusing anecdote about the Haiti Kid and one of the Frenchman's testicles." (Hogan's My Dad)
From what I have read, this MP3 issue has existed for a while - so rolling back *may* not necessarily fix my problem. And I should mention that none of the files that I'm having issues with were ill-gotten gains.