Will not connect to any Internet

I have a MacBookPro running OS X.

I have full bars on my wireless signal but it won't connect to the internet. This is across all programs. I've been on this network for over a year with no problems. Another mac in the house, a PC, and an IPhone can all connect without problems.

Here is a list of all the troubleshooting things that haven't worked:

*Restarted computer, router and modem.
*Reentered password.
*Renewed DHCP license.
*Tried connecting to a different network, including an unsecured one.
*Cleared browser chaches; tried three different browsers.
*Pings come back with 100% packet loss.
*Tried a few numeric IDs.
*Tried an Ethernet connection.

I have no idea what else to do, and I'm trying to keep the Mac store a last resort as my Apple Care expired--literally--one week ago. Any suggestions?

So even with a hard wired Ethernet connection you get the same result? If you open System Preferences and Network and click on say your Wired connection what IP Address is showing?

The Ethernet hook up generates the same (self-assigned) IP as trying to connect via wireless. The IP it shows is 169.254.7.75

Just for a test, make a new account and log in to the new account. Do you still have the issue?

I'm not sure what you mean by new account. In Airport if I make a new 'location,' I still get the same problems and IP addresses for both my WAP-secured network and the unsecured network I have access to.