Exactly the same issue. 4S, firewall off or on, restarted my AP Extreme, devices, laptop.
The syslog is filled with these lines:
9/20/12 10:15:22.848 PM mDNSResponder[36]: ERROR: handle_resolve_request bad interfaceIndex 1
...
9/20/12 10:15:22.996 PM mDNSResponder[36]: ERROR: handle_resolve_request bad interfaceIndex 24
9/20/12 10:15:33.670 PM iTunes[2010]: AVF KeyExchange Version from driver for Certificates 1
9/20/12 10:17:34.385 PM iTunes[2010]: _receive_message (thread 0x116bda000): Could not securely receive message size: SSL_ERROR_ZERO_RETURN
9/20/12 10:17:34.385 PM com.apple.usbmuxd[1212]: SCEDeviceSocketCallback 0x1020062a0-iTunes/com.apple.iTunes remote peer closed connection for sce 0x1020062a0.
9/20/12 10:17:34.469 PM iTunes[2010]: _send_message (thread 0x116bda000): Could not securely send message size 406: SSL_ERROR_SYSCALL errno (Broken pipe).
9/20/12 10:17:34.470 PM iTunes[2010]: AMDeviceStopSession (thread 0x116bda000): Could not stop session with device 3: kAMDSendMessageError
9/20/12 10:22:27.158 PM com.apple.usbmuxd[1212]: SCEDeviceSocketCallback 0x1020037b0-iTunes/com.apple.iTunes remote peer closed connection for sce 0x1020037b0.
9/20/12 10:22:27.158 PM iTunes[2010]: _receive_message (thread 0x7fff7b70e180): Could not securely receive message size: SSL_ERROR_SYSCALL (Early EOF reached)
9/20/12 10:22:27.577 PM iTunes[2010]: _send_message (thread 0x116bda000): Could not securely send message size 406: SSL_ERROR_SYSCALL errno (Broken pipe).
9/20/12 10:22:27.578 PM iTunes[2010]: AMDeviceStopSession (thread 0x116bda000): Could not stop session with device 3: kAMDSendMessageError