My neighbor and I each use an Airport Express on different ISPs, so that we can 'borrow' each others signal when our own has gone down. There are four Macs in my house and each receive both signals fine, but my old 667mhz Tibook keeps dropping the neighbors signal intermittently, while still receiving mine. The drop out is usually only for five seconds or so, but it is enough to disturb downloads, AIM, etc. The usual 'three bars' just drops to zero. I know its not a reception problem (common to early Tibooks) because it has a good external antenna. Has anyone else had this problem? 