Why cant my computer connect to facebook, youtube, twitter etc?

[she_woman_cat_type_thing]

It always comes up cannot connect to remote server, People have suggested clearing cookies, cache, disabling firewall etc, just doesn't work. I can Connect to other websites, But social networking such as facebook, twitter just come up with cant connect to remote server. I am an adult, so these websites are not blocked under parental controls or anything, I just want to know why they dont work on my computer? They work fine on my phone on the wireless, just not the computer? Why? My phone and internet both use the same wireless connection? Also youtube only works sporadically on my computer.
Its the same with all browsers, IE, chrome, opera, firefox etc
I have run virus scans, My computer is fine, Just wont connect to these specific websites. I wonder if its something to do with the router.
Been there, done that. Thanks anyway.
This is the same for every computer in my house, My laptop, My sons netbook, 2 old laptops and a desktop computer. But not mobile phones on the same wireless network.
Thanks Jimmy cool, but my computer works fine, I don't want to needlessly download expensive and potentially harmful software to correct what is probably a quite simple problem.