This is a simple CGI script for OpenWRT Backfire (Kamikaze should work too, but I have not tested this) to allow reconnecting to the Internet without any authentication.
Download reconnect to /www/cgi-bin and make it executable by entering
wget -O /www/cgi-bin/reconnect http://github.com/matthiasr/openwrt-reconnect/raw/master/reconnect
chmod a+x /www/cgi-bin/reconnect
Open http://192.168.1.1/cgi-bin/reconnect and click Reconnect (substitute your router's IP if appropriate). Your WAN Connection will be torn down and re-established.