I don't know either of those devices but do this quite often with surplus ISP provided routers.
Try the following ...
Connect the Netgear to your PC directly - with nothing else connected. Access the user interface and then Turn Off DHCP server. Then give the Netgear a fixed IP address - just outside the range the Buffalo will allocate.
For example: Buffalo 1ill have 192.168.1.1 to 192.168.1.64 available to assign and will itself be 192.168.1.254 so fix the Netgear at 192.168.1.99
Save, Save and Save, then reboot.
Connect Netgear (port 1) to the Buffalo using a standard ethernet/RJ45 patch lead.
Connect to the Buffalo using a wired connection and then in a browser try to access the Netgear at 192.168.1.99 if that works you can talk to it "wired". The set up the Netgear's wireless as normal.
M H C
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