My MBP just had the strangest problem I've ever had on wi-fi. First of all, instead of connecting right away to the network as soon as I opened the computer, the wi-fi icon on the kept showing that it was trying to connect, and finally couldn't. I turned the wi-fi off then on again, and after some searching the icon showed it was connected--but in fact I wasn't connected, so no internet came through--although the AirPlay icon showed that it was connecting to the AppleTV. I restarted and still no joy. So I after repeating everything a couple of times, I went to the Network Pane, duplicated the Wi-fi connection, and then turned off Airport. The pane asked if I wanted to save the duplication, I said no--and then when I turned Airport back on, presto change-o, I was connected to the web. I haven't restarted, or put the laptop to sleep yet, so I don't know if this is going to repeat. I hope not, because I have no idea why what I did worked.
MACTECH ubi dolor ibi digitus