I have Sygate Firewall software which I'll use whilst the router isn't working. I did try entering some DNS servers manually via my network settings for the laptop and it didn't work, even without the router.
It started to work again after a firmware update, but I've just come back from a meal with the Mrs and its broken again and I'm back to the NTL cable modem only.
I'll try the suggestions and let you know (its been about 4 years since I did any IT work and its showing
)
/edit - Just checked the DHCP is ticked on the router and has the DNS addresses you have already there. I've manually edited the IP settings on my laptop and also put in those addresses.
Its working again now, but don't know for how long as thats the only change I have made.