Open Command Prompt and type "ipconfig /renew", if you're still banned after the first try, type it again.

If that doesn't work, try these steps:

Go to your router's page (192.168.1.1 by default, could also be 10.0.0.1 or 192.168.0.1)
In "Status" or "Setup" menu hit "Release IP" button. Save settings
Disconnect the router from modem
Remove batteries from the modem and disconnect AC cord (DO NOT TURN OFF THE ROUTER). Leave it for couple minutes
On your router's web page find "MAC Address Clone" function and change your MAC address to whatever you want (only numbers 1-9 and letters A-F). Save settings
Plug in AC cord in the modem and reconnect it to the router
On your router's web page hit "IP Address Renew" button and new IP adress will be assigned to your router
Enjoy your aids.