I reformatted my macbook pro with Snow Leopard installed about half a week ago and it has stopped connecting to our wifi. The icon it shows for wifi is no bars with a '!'. It sees our internet in the menu bar but fails to connect properly. I have tried resetting the PRAM, that does nothing. All other computers in the house can connect to it. I've tried turning the laptop, airport and our house's internet off and on again. None of this has worked. Any ideas?