This might help:
http://www.nintendo.com/consumer/wfc/en_na/routers/Netgear/WNDR3300.jsp
It says:
"These routers are set to "Up to 150 Mbps g/n" mode by factory default. This mode may not be compatible with Nintendo systems. Our experience has shown that for these routers you'll need to change this mode to "Up to 150 Mbps b/g/n" or "Up to 54 Mbps b/g/n." The mode setting is found in 'Wireless Settings' under the 'Setup' section."
If this does not help, contact Nintendo here: