If you use win 2000/XP/Vista try this
go to
RUN (windows key and R)
type
cmd and click OK
type
ipconfig /flushdns then press
ENTER
wait until it finishes
try browsing..
If it works, it's because the previous DNS cache was via a Proxy server, which may still be there, but you are no longer automatically being forced to use it.
If you try using a "VALID" proxy, by adding it via LAN Settings, you will probably see a VM page that tells you to remove the Proxy from LAN settings, you won't be able to browse until you remove the proxy.
There is "rare" logic in the reasoning behind VM removing the proxies from broadband connections. The Proxies were overloaded and prone to issues with secure sites etc, many of them were designed for dial-up 56k connections originally, ntl:/VM tech support used to take many calls from customers with browsing issues due to bad proxies.
I'm afraid that without Proxies, browsing to sites that you visit for the first time may be slow, but the temp internet files on you PC will help alot, try keeping the temp internet file settings to < 100 MB or you'll end up with problems later.
Oh and if sites don't load first time, try
ctrl and
F5 which will refresh the page from the original server and then refresh your temp internet files for that page properly.
I used to work for Virgin Media, but I'm 
K Now