Windows 7 browsers unable to resolve domain names

A few days ago a client's laptop just stopped connecting to the internet via the browser.
The laptop is a Dell that is only about a month old running Windows 7 with no software other than firefox  that isn't Microsoft's. All the lady does is browse the web and get eMail so she has no inclination to add any more software.

When she got it, she called me to set-up her network which includes an HP printer and her computer on a wireless network with a D-Link router.

I uninstalled Norton (through add/remove programs) and installed Microsoft Security Essentials.
I also installed Firefox (although she only uses IE).

I also set-up the network and everything was fine running perfect until 3 days ago when she couldn't connect to the internet through IE.

She called SHAW Cable Support who monitored the connection, saw her router was getting an IP and communicating but had no idea why she couldn't connect so she called me.

Typing any domain name into either Firefox or IE would not connect, (Site could not be found)
IPCONFIG is good. Has been released/renewed, and I even tried changing the DNS server from the gateway to the ISPs
In all cases NSLOOKUP, PING, TRACEROUTE are able to resolve the domain name and return the IP.
The DNS client is running.
Neither browser can resolve domain names.
Both browsers work fine if I enter the IP address, the problem is with name resolution.

I thought it might be remnants of Norton left on the system so I used Norton's own 'Complete Removal' system to remove all traces.
It left no files/folders/registry entries and indicated success.
After a reboot... still same problem.

Windows network diagnostics indicates that it cannot find the problem.

I verified that no proxy was selected.
I disabled Microsoft's firewall.. problem still present after reboot.
I checked the HOSTS file.. intact but no entries.
 * I actually tried adding an entry for google.com into hosts to see if that would work but it didn't.
I tried booting in safe mode with networking.. still no name resolving on either browser.
I reset winsock (netsh winsock reset)... that did not fix the problem.
I thought maybe IPv6 problem, disabled that protocol.. no change, problem still there.
I also toggled network.dns.disableIPv6 in Firefox's about:config screen and tried that to ensure IPv6 was not the problem... no change
I flushed the DNS 'ipconfig /flushdns' several times through this and at no time did it make a difference.

I rolled back to before the last update (at which point the system was working) and still have the same problem.

Other than re-installing Windows which means I would have to set up the network and MSSecurity again, I have no ideas.
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Any ideas?
  - Kent