I have the Netgear DG834GT and am with Virgin when they upgraded their speed I did nothing and it continued to work as before.
I didn't see any great speed increase because of the distance from the exchange but I knew that would be the case.
I am using wireless to conect both my desktop and my laptop. Can you enter the orginal settings manually:
IP Subnet Mask
Gateway IP Address
Domain Name Server
Or reinstall the router using the original disk.