Self-assigned IP address

it means that your pb cannot obtain an ip address from the wireless access point

this could be a hardware or configuration problem with the pb and/or the access point

i know that's not the most helpful of answers!

do other computers connect ok to the access point?

does the pb connect ok to other access points?

have you installed a software update or made any config change since the last time it worked? some people do report wireless problems after updates

try rebooting the wireless access point/router to see if that clears the problem - some seem to have problems after long uptime or heavy use

try using the 'create network' option in the airport drop down menu, and re-enter the network name, security type, and password

if these things don't make a difference, you need to give some more info to see if that gives some more clues for a fix...

what model wireless ap/router are you using?

is it running in b, g, or bg mode?

has it's config been changed/lost?

what security are you using? - wpa, wpa2, wep (gack ptuii), none (same as wep...)