I bought a new router and could not get an open nat type with it like I had with my old router. I tried a lot of stuff, with no joy. Then I ran across the Nintendo website, which gives very good directions, followed everything in the directions an now have an open nat type. Hopes this helps anybody that still don't have an open nat type.
http://www.nintendo.com/consumer/wfc/en_na/ds/results.jsp?error_code=86420&syste m=Wii&locale=en_US