Quote (AnimeFTW @ Aug 23 2011 02:35pm)
It could possibly be an issue with your host file. If for some reason you have typed youtube's address in the file, it will block the website.
You can check this file at C:\Windows\System32\Drivers\etc\hosts
Open it with notepad and see it youtube is among the blocked sites.
do this again BUT this time do this before:
click on tools - folder options (control panel - folder options if vista/7)
then click on the view tab - show all hidden files and folders
then navigate yourself to the folder
there's a common virus that hides the "malicious" host file with the original name (hosts) and renames your original host file to something similar (you can't really see the change) and leaves it visible
if this isn't it, try to open your browser without add-ons
if not, click on tools - options - advanced - network - connection - settings - make sure there's no proxy
if not, start - run - type cmd and press enter
type in ipconfig /flushdns
try disabling your anti-virus/firewall for a few minutes to test if you can access the websites
that's all i got :/