I, too, am having issues connecting to Nintendo WiFi through my wireless router.
I had no problems assigning a static IP to my DS's MAC address, and logs confirm that my DS does connect to the router and get the IP I've told the router to assign to it. However, when I test the connection on my DS, the error it reports is that it could connect to the router, but, not through to Nintendo WiFi from there.
I tried unblocking all the ports that Nintendo WiFi recommended, and fowarded them to my DS's address (Forget which ports offhand, there was about 6 TCP ones, and it wanted ALL the UDP ports unblocked too), but, to no avail. I even tried putting my Nintendo DS's IP into the DMZ (De-militarized zone), with no change to the symptoms.
I've contacted D-Link about the issue (My router is a DI-524). Hopefully they will have some solutions for me. If not, I've read instances of people whining at Nintendo about their router not connecting, and rather than investigate the issue, Nintendo just sent them a free USB transmitter to do the job. Perhaps this will be my next course of action
