Belkin G Plus MIMO Connection Problem

I have a Wireless Belkin G Plus Mimo router and I had the password security settings set on WPA and it worked fine. I then changed it to the 128bit WEP so I could use WIFI for Nintendo. My USB Wireless thing for my Desktop downstairs wouldn't connect so I decided to change it back to WPA and now I can't even get online. The only settings I changed were the security settings. Can you people help? I can still get on the router's setting by using the IP but I can't get a connection. Right now I'm using the router comcast gave me.