Just wanted to add my 2 pennies as I have the same problem here with 29 and 30 and same explanation as Intodevel on how to replicate.
Personally, I downgraded to v28 and disabled auto updates.
You can do this by visiting https://ftp.mozilla.org/pub/mozilla.org/firefox/releases/28.0/ and installing the correct version for your OS.
To disabled auto updates (essential if you don't want Firefox to revert back to v30 after it's restarted) click the orange Firefox button > Options > Advanced (cog icon) > Updates (tab) > Then select "Check for updates, but let me chose whether to install them"
EDIT: Also, be sure to disabled "Use a background service to install updates"