When I leave the house carrying my iPhone, our Wi-Fi network stops being available, and the people left in the house have to restart one of the access points to get back online.
We're using two Airports Express, connected to each other using WDS. The Wi-Fi network is using WEP encryption. My iPhone is an iPhone 4. The Wi-Fi network has three Macs and one PC connected to it.
What specifically happens is that the SSID for the network stops appearing in the list of available networks. The 'WDS relay' Airport Express starts showing the orange light. Restarting this Airport Express is enough to bring the Wi-Fi network back up.
I was skeptical when I was told this was happening, but we've tested it, and it is a reproducible problem. Once I get a certain distance from the house, the Wi-Fi network dies. It's so weird that I'm at a loss as to how to diagnose the root problem, so hopefully someone here has some inspiration or has encountered something similar before.