Hello Twiglet, how bizzare... have you tried the openDNS solution?
www.opendns.com/start
It is very very easy to set up.
Go to your
control panel:
double click
network connections
choose
properties
scroll down to
Internet protocol (TCP/IP) and highlight that
click
properties button below
You will see two sets of boxes one for IP address
(which you don't need to touch)
and one for
DNS server address.
Make a
careful note of the numbers in these boxes, in case you want to go back to the original setting
It is quite likely that the two sets of boxes will be empty, and they are set to "obtain an IP address automatically" and "Obtain DNS server address automatically"
Click the button to change to
"Use the following DNS server addresses:"
put the following numbers in the boxes:
208.67.222.222 and
208.67.220.220.
Those are the domain servers for OpenDNS,
click okay, restart your computer.
Connect to the internet you should be able to see the world. If you can't go back to the network connections and change the setting back the way it was before.
Before you shut the computer down, make sure that you have kept a copy of these instructions, either printed or copy paste and save into note pad or similar.
If you have done this all already, and it makes no difference, I am stumped.
I have tested openDNS it works very well, and some cool features that you can play with at a later date.
You don't need to register to use the service
I hope that is helpful to you Twiglet or someone, if not sorry
So don't go panicking if you don't hear from me, Annpan!! 
( am I prone to panicking?... oh dear... too much coffee)
)
