I've ran into two problems several times recently and thought I'd share the quick fixes.

Problem 1: ethernet cable is plugged in but won't obtain a DHCP lease. all the usual hardware troubleshooting won't change the yellow dot to green. Same problem can occur for airport also, can join a network but not obtain a lease/ip.

Solution 1: delete the network interface. then you can either do something to make it see the new interface and add it (such as reboot), or just [+] add it yourself. the new interface will dhcp fine.

Problem 2: airport won't accept password for some or all networks you try to join

Solution 2: go into airport settings and locations, add a new location called "DHCP', using all default values. Delete "Automatic". Apply changes. You should now be able to join all networks again.

fyi, in case 2 you will see something like this in the console logs: Error joining xxx: Invalid password (-3924 Invalid master key)”


I've seen almost a dozen case 1 and two case 2 with 10.6 recently.

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