Is this a DNS issue? Can you resolve the DNS names correctly?
I assuming you have your router configured to be a DHCP server and hand out IP addresses and relavent DNS details, did you make any changes?
With NTL/Virgin their DNS servers seem to be increasingly broken (google, hotmail, ebay and BBC seem to be the most frequently broken) and I've changed to manually entering alternative DNS servers in my routers DHCP settings.
Link to nslookup doc if your not familiar with it's use.