The problem is usually caused by a failure of the DNS lookup system supplied by your internet service provider. There are many workarounds including using a proxy address such as: http://anonymouse.org/cgi-bin/anon-www. ... z/coventry but the simplest cure is to change the address of the DNS server you are using from the one that your ISP gives you to one supplied by a third party. The two most popular (and completely free) are Google Public DNS and Open DNS.
The precise details for changing the address are different for each operating system and each version of Windows so I can't reproduce them here but there are many guides on the internet including these:
The Ultimate Guide to Changing Your DNS Server
How to Switch to OpenDNS or Google DNS to Speed Up Web Browsing
How Do I Change DNS Servers?
How can I change my computers DNS address?
Or you can simply Google "how to change change dns"
Note that changing your DNS address may give you access to other websites that you could not access before including some that your ISP may disapprove of for political or commercial reasons.
It's not as difficult as it sounds, needs only to be done once for each device and in my experience is well worth the effort for the extra freedom to browse the internet that it brings.
