I guess in your case, the 4 bars on the Airport icon were present, right? I was talking about "normal" IP address, not out of range. In this case one can do a lot of logical tricks like resetting the router (hard and soft), resetting the modem, restarting the computer, and then something suddenly did the trick. But no real advice, like do this and it will start working. I also noticed that my clever Belkin router would show "not connected" with no obvious reason, while the MBP comfortably said that it was connected, with the right IP address and the same 4 bars on Airport. In this case, no connection was there, obviously, verified by Internet diagnostics utility. What is happening in those moments, beats me. A router restart, a modem restart, both restarts would suddenly make it work. I wonder why the TCP/IP does not sense losing connection.
BTW, manual IP never worked for me over several OS renditions.
