have you played about with the firewall and ip flood detection? ip flood detection should be turned off and the firewall seems to be behaving differently for different people, so just change it to the opposite of what it is on now (i.e. if its on, turn it off)
i presume you know how to access this,
http://192.168.0.1
default username: admin
default password: changeme
(if you have changed the above, obviously it will be different)
once you have logged in, you will see three big red buttons, click the link under this for "advanced settings" the "services" on the left, and the firewall and ip flood detection are tick boxes on this page