I think it has to do with the Wii browser. I notice that it started slow but once it got in youtube everything else was OK. Have you tried putting it back to the Default DHCP and see it got any faster? As of right now I'm testing all this using the Wii broswer. In other words I'm entering this in using the Wii Browser. Oh the Wii browser got updated like a few weeks ago I believe.
Update: I figure it out. The wii has issues when the MTU size is set to a certain size. This is understandable as the perfer way is always auto. When the browser first is launch it has hard time extablishing a internet connection due the MTU. The same goes with the Nintendo Channel when it is trying to update. After a few more tests I figure out that the auto setting Nintendo has is listed as number "0." With it set as the MTU it fixes eveything. It makes since as a MTU size can never be zero. If it is then no data would be able to sent out meaning no internet connection. So in other words issue fix with Wii browser having a slow startup with first webpage. Also it improves Nintendo Channel updating when first launch. Try it and let me know. Again I'm using the wii browser which is working a lot better since the last update. We I do know is that Wii processor and the Browser is not writen where they work in perfrectly which is why the browser is a little slow. Thats something we can't fix. I say it's not written/program is because I know the wii can do a lot better then this. Just look at the IPhone or Blackberry.