I had this problem as well, and tried everything (Factory reset laptop, ipconfig stuff, yadda yadda yadda) What was the culprit? The Motorola modem from Comcast. It (old and Motorola, so...c'mon) won't work with the (new) Apple Express Airport. Comcast sent me a new modem and everything worked.
I hope someone reads this and thinks about the various components and they're shelf-life.
I hope someone reads this and thinks about the various components and they're shelf-life.
