From the Nintendo Tech Forums:

1. Follow the installation instructions TO THE LETTER! D-Link products tend to be very temperamental during the initial setup stage - just allow it to configure all the defaults for you.
2. Make sure you use only WEP encryption. Yeah, I know, older then your granny's socks, but Wii does NOT play nice with WPA on D-Link products. It will work, but connection will be lost after extended period of inactivity.
3. Leave protocol on "mixed n/g/b" ("n" will be disabled with WEP)
4. No need to select a channel - let router select one for you as well (mine selected 11)
Otherwise, great router for the price. Wii and DS have connected flawlessly on the first try. A week later - still did not have to reset the router. I have verified in the router log - Wii connects on 801.11g protocol, DS on 801.11b - both fast and stable.