169 IP Address...AAARRRGGGG

well, i am a tech for a company and i do a lot of networking...mostly ADSL. i have read several threads/blogs about people starting to have this problem. what i have noticed is that there was an auto update from MAC on April 27, 2010, and i have been getting a 169 ip address ever since. i can go to PPPoE and manually put in an address like 192.168.1.150 and sometimes it will work. this problem started on April 27th with my Macbook. i also have a MAC desktop that still works fine in DHCP pulling a 192 ip addy, both using airport. my desktop didnt get the update. i have compared all of the settings i can find between the two machines, and cannot find a difference. if there is anyone who can help, it would be appreciated. as of now, i cannot even put in a PPPoE 192 address and get it to connect.

I use to be a ADSL tech, still work for the same company but I other things now.

Try assigning a static IP on the problematic computer.
DHCP should work, but a 169 ip means the computer is not obtaining one on it's own.

I would also try power cycling your airport, while it's still set to DHCP.

What is your network setup? What do you have as a router? Do you have any repeaters?

I've found when I get a 169 self assigned it usually because my Airport Express crashed - I can connect to it but the Express isn't connected anywhere. My DHCP server is a netgear router so since I never get to it I get a self assigned IP.