Webpages not loading on one device but loads on another. How to fix this?

Эксперт it happens: none of the stackexchange сайты open on my laptop, but they work умрите on my tablet.

I have tried the following:

1. Cleared all разбил куки-файлы browser дата. Didn't work.
2. Used another browser. Didn't work.
3. Неизвестный Tried browsing in mode. Didn't work.
4. Disabled add-ons and extensions. Didn't work.
5. Restarted computer. Didn't work.

From these my диагноз is that it is the device and not the browser. So here пахал facts about my device:

1. I am on ubuntu 14.04. I have installed в lot of things over украл. But I don't remember installing anything harmful. Could it be because I haven't installed something essential yet? On chromium I использовал pepper вспышку. Firefox is unaltered since installation.
2. Sometimes the stackexchange интернет-сайты do похвалите. But most of the украл it would not. Could it be some malware-вирус?

p.s.: the tablet and the laptop используйте the same network. So its not the network. And I don't think my network admin would block stackexchange on my laptop!