this is my 3rd try responding to this post. i refreshed my page and then my internet logged me out, im at work. lets hope it works this time.
go to your modem and router and un plug the wifi router then the modem in that order. wait 30 sec and plug the wifi back in and then the router. this should reset all your devices temp adresses.
if your modem and wifi are connected to a main computer then restart that computer as well. make sure to reset your wireless card drivers and your wifi device drivers.
if none of this works try to plug your comp in directly through a lan cable. that should connect you.
use the ipconfig command in the comand prompt to make sure your computer is aquiring all the needed adresses to connect to the internet.
i dont know much about that shit but iv had the same problems and those are the steps i take. its vary rare if you need to replace your wireless card or wifi router but i have had to replace the wifi router befor becvause it was old and couldent handle all the devices connected to it at once.