I am suddenly having problems with my MacBook Pro's wireless connectivity. It has worked flawlessly up to this point: I choose a wireless network from the list, I type the password, and it just works. Now, all of a sudden, I am not able to connect to any wireless network. My computer tells me I am connected to the wireless internet network I chose, though the Network window says that the airport is not connected. No webpages will load, and I cannot access the iTunes store. I have tried to follow some simple problem solving after doing some research, but I am having no luck. I am somewhat computer illiterate and I really need my internet to work. I haven't changed anything, so I am at a loss as to why it would fail suddenly with no warning. HELP!