Weird Airport Problem: Self-Assigned IP Address

Very frustrating...

http://discussions.apple.com/thread.jspa?threadID=2322497&tstart=90

The final solution that works:

Deleting

• /Users/YourUserName/Library/Preferences/com.apple.internetconnect.plist
• /Users/YourUserName/Library/Preferences/ByHost/com.apple.networkConnect.<12>.plist
  

saves the day!

/Library/Preferences/SystemConfiguration/com.apple.airport.preferences.plist


To read:

Tutorial: Preferences Files: The Complete Story

Preferences Files: The Complete Story (Part V); How .plist files become corrupt and troubleshooting the results

from CNET macfixit