You're on a very old version of Firefox which has security flaws. I recommend updating to the latest Firefox in order to stay protected. Current version is 45.0.2. I would not suggest staying on an outdated Firefox version.

You can download the current Firefox version at https://www.mozilla.org/en-US/firefox/all

Nonsense, version 40.0.3 is only a few weeks old, why I stay with versions a few weeks old is not relevant. I've tried previous versions of FF prior to this one, same problem, I've tried 45, same problem. Likely therefor that problem is something perhaps in registry or one of the parameter files in FF.

Firefox 40.0.3 (forty.zero.three) came out months ago on August 27, 2015 as you can see at https://www.mozilla.org/firefox/releases/

It is not an ancient version however it is not new either.

Sometimes updates may not get applied and you need to manually download and install new version.