It's you, Stephen--we've had FIOS since it was available here--no problems, it NEVER goes down (unlike comcast) and the Wii works great. Yup, it must be you! :biggrin:
If you want the DS to work, there are 3 options that I see:
1) reduce the sercurity on the network to WEP or nothing (NOT reccomended, but easy)
2) Use the Nintendo Wi-Fi adaptor (which has been discontinued: http://www.nintendo.com/consumer/systems/wii/en_na/onlineUSB.jsp) or the equivalent. (Easiest, with security)
3) Use another router to segment out the DS network. (more complicated, but if you already have another router it would be the cheapest).