No, that is not what he meant. Remove the password doesn't take away the lock, it just makes it so there is no key. You have to set your Security mode to "None" then save the settings. I have a feel it won't even connect then. I quote
Nintendo support site: "Network Speed Compatibility
802.11a, 802.11b, 802.11g are protocol for exchanging data, with the letter designations indicating network speeds. In order for the Nintendo DS to be compatible with your router, the router's Network Speed
must not be set to just "g." Set your router to "mixed" so that it is using both "b" and "g" settings."
So you have to set your 802.11 mode to mixed N, G, and B. That is going to slow down the rest of your wireless network though. And there is no way of broadcasting the guest zone as a different 802.11 then your main wireless so your kind of stuck. Your only way is to either accept the decrease in wireless speed, or buy a AP (probably a cheaper B/G one) and connect it wired to the DIR-655.