I'll try and offer some help. In your post you didn't specify it was happening while trying to play online or initially wasn't clear(but I'll assume it was initially).
Configure Your Wii To Use Wireless.
From Channel Page click the Wii button on the bottom left.
Click Wii Settings and hit the + sign on the Wiimote once.
Click Internet and then Connection Settings
Select an available Connection1-3 (doesn't matter)
Click Wireless Connection and then Search for an Access Point
Choose The access point you want to connect to.
Enter your encryption key if you have one (I think it's case sensitive also)
And finally attempt to connect.
Try and keep your settings even if they don't work at first.
(In other words don't delete your connection settings if you can help it)
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Had to get that out of the way, never know?
If that doesn't work there it's definitely the router. Some routers limit the amount of connections they can handle I've had one where it could only handle 4 connected devices including wireless it's important to check documentation which can usually be found at the manufacturer's website(in other words google it).
Every router is different but according to the default setup to your router. You would need to open up a web browser and enter 192.168.0.1 (according to portforward.com).
The default login to your router is with a username of admin with no password<------BAD!!!!!! this comes from (
http://www.phenoelit-us.org/dpl/dpl.html).
If you cannot login you'd have to ask your network administrator or someone who knows. If you can't find the login creditials you'll have to do a hard restart (usually a small button on the back of router that can be only pushed with a pin or pen) which might include re-installing software to program the router to access the internet through your ISP.
I wouldn't do a hard reset if you don't know what you're doing!
From the router configuration page I can only give generalities of what to look for because I don't have knowledge of the DI-524 router and many other routers...lol
Wireless > Turn Off Any Encryption or MAC Address Filtering
Firewall > Disable It
DHCP > Make sure it's still enabled and has a big enough range of IP addresses to give your devices.
Attempt to connect again with the settings created at the beginning of the post.
If that doesn't work you might have to configure your Wii manually(which i can attempt to help you with and is better) or invest in a LAN adapter.
(As far as I know Nintendo has discontinued the USB Adapter and might not offer support for it much longer.)