You may wish to try Minefield, (4.0 beta) if you can stomach using a beta. I've actually been using the nightlies for months and they're generally stable. You may want to try a release beta, however. (4.0b6 is good). There are 64-bit linux, Mac, and Windows versions.
Keep in mind that it's a beta, though and not intended for general consumption quite yet.
http://www.mozilla.com/en-US/firefox/all-beta.html
Because I hate Flash, I have a separate Firefox profile specifically for using the plugin. (Yes, there are other ways to block flash, but that isn't helpful if you're trying to find which of 200 tabs started autoplaying on startup)