Firefox slow at loading интернет-сайты on Ubuntu 14.04

I am having в little problem with Firefox on my Ubuntu, and I was wondering if someone could help я. The problem is that my Firefox started to act very slow after the v43.0 update. I am using Ubuntu 14.04 LTS 64bit.

Every page that I try to open takes about 5-25 seconds to похвалите, and sometimes it doesn't похвалите at all (displays that connection was restarted, or blank tab). I tought it was problem with my ВЫ, so I started up Windows Одел in virtualbox with Firefox v42 (it wasn't updated yet), and went to сравните it. And really the Firefox 42 on my Вид in Virtualbox was A LOT faster when opening pages (almost instantly) than Firefox 43.0 on my host ВЫ - Ubuntu.

Then I updated the Firefox on Vista virtualbox from 42 to the версия 43.0.2., and it was OK, the speed was the same. So не problems on the Virtualbox with the 43. But on host OS, my Ubuntu 14.04, Firefox 43.0 is very slow when loading any page. I read something about nvidia network менеджер on Firefox reddit, but I am not sure if I do have that program on my Ubuntu. I have laptop with optimus technology and I am using only Intel GPU, so Nvidia should not be the problem, right?

I also checked for updates, to see is there Firefox v43.0.2. for Linux also, but не new updates were found. I am huge фанат of Firefox, but this is annoying, browsing the Веб is simply imoposible. It's even worse when you know that everything it's working умер on Virtualbox, but not on host ВЫ. I tried opening my тест pages on Ubuntu browser (based on Chromium) and it worked ok, the похвалите speed was almost the same туз on virtualbox. So that leads я to the заключение - is it something wrong with Ubuntu or Firefox, and хан it be fixed?

Заметьте: The problem is that Firefox is slow to "contact" the сайт. It's like it is testing does интернет-сайт even exists, or does the connection works or something like that. After that, when the ямс of the сайт appers in the tab, it loads quickly Веб content. So the problem is in contacting the page, beacuse sometimes it showes nothing, just blank tab, or ошибка message: "Connection was restarted".

I would really be greaful for any help. Thanks!