oberder wrote: 
Head's up -- Mozilla has now released Firefox v30.0, and is ready to install via the browser's updater; it's offline installers are available at the publisher's official downloading section, as well as reputable downloading hubs; for those that need the regional variants of Firefox that uses your local dialects, visit the publisher's downloading section; below is the Release Notes in regards to the new update:
Hey
oberder,
Do you have any Conduit toolbar (from ClixSense or any other site) installed on Firefox? I was on FF v29 till morning and everything was fine. Then I noticed Conduit updated all their toolbars earlier today.
In the afternoon I upgraded my FF to v30 and ever since I have a really weird problem. The
+ button to open a new a tab or the shortcut Control+T (Cmd+T on Mac) to open a new tab will not work.
I thought it might be a bug so I tried searching but no one else reported it. I decided to disable all my add-ons and enable it one by one to see if one of them was causing the problem. Eventually, it was a Conduit toolbar which was causing the New Tab issue. I disabled the toolbar and bingo everything is normal again.
So if you have a Conduit toolbar, please check and let me know if you face a similar issue.