i have that model router. my Wii will not connect to it either.
i've had to use a WRT55AG (wifi router) as an access point
for the Wii to connect to.
go to the linksys site to see if there's an upgraded firmware
for your variant of the router.
there are also other firmware versions available from people who
have modified the original linksys firmware.
mines a v.5.x so i can't flash it with one of the "hacked" firmwares
which are available for this model of router.
if you're unsure of the version you're using, have a look at the
bottom of it for version details.
for indepth info re: linksys routers, head over to:-