I can't add a password for my WiFi?

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I've tried everything I can think of but still can't add one. It actually used to have a password on it, so I'm not sure why it doesn't now and why I can't add a new one. I have a MacBook (2009, OS 10.6.8), and I've tried going into network settings and adding a WEP password, then a WPA2 Personal password, etc. They say they've added, I save the settings, but then I click the AirPort icon and there's still no lock icon next to my network. I've tried to access my IP settings by typing it in as a URL in the address bar, but Google Chrome says it can't connect. Tried again in Safari, but the same thing happened. So how can I add a password? Thanks.