Do you have other devices connected wirelessly that are working? Maybe check their settings and try to duplicate them for the Kindle. You may have to check the router settings themselves. Do you have the manual for the WBR-100 so you can check if DHCP is enabled, SSID is being broadcast, what the the correct security password is (people have reported problems with characters being used as well as two word passwords), MAC filtering is off, etc? If not here is a link to that manual:
Hope this helps.