Why do Twitter, YouTube and Facebook stop loading after a while?

[Jasmine]

I've been having this problem since last month. When I first start my computer, all three sites load fine. After a few hours, the error page comes up stating that Google Chrome (my primary browser) can't load the page. A few weeks ago if I switched over to Internet Explorer, the sites would still be able to load. Now the sites don't load after these few hours in any of my browsers. I've done virus scans, malware scans, cleared the cache and everything. Why would this be happening?