I've just switched from an iMac to a MBA with external monitor. I've shifted my iTunes library and have authorised the new computer in iTunes, etc. Both my iPhone and iPad have the "synch via wifi" option selected. Both are on the same wifi network as the MBA (just like the iMac was). However, neither device shows up in iTunes if I unplug the cable. With the cable plugged in, everything works as normal and I can synch. When I unplug the cable, the device disappears and iTunes can't see it. With my iMac, both the iPad and iPhone were listed under devices, no matter where they were in the house, so long as they were on the wifi network. I think I've been through every iTunes setting (the "prevent ... from auto-synching" is NOT ticked). Running iTunes 10.5.3, Lion 10.7.2, and iOS 5.0.1. The MBA is in clamshell mode with the external monitor connected, and is on the wifi network without any problem. Any ideas? Am I missing a step somewhere?