Find my iPhone works everywhere except at home

I've got a 3rd gen iPod Touch and an iPad. I've installed and configured the Find My iPhone app, but it doesn't find my devices when I'm at home on my Apple Wireless Network (Time Capsule). It lists the devices, but is unable to locate them. Other apps that use location all work on my home network.

The Maps application can locate them. OmniFocus app can locate them. If I take my devices to the WiFi umbrella at work, then Find my iPhone can locate them. When at work, I can send messages to them and lock them up, so I know the mobile devices are configured correctly.

So, what is it about my home wireless network that won't let Mobile Me locate my devices at home?

Any advice appreciated...

Find my iPhone fails at home

I turned off the Firewall in my DSL Modem, and now Find My iPhone can find both my iPod Touch and iPad.

Interesting that the Firewall didn't break Location Services for other apps on my devices. Also interesting that turning on the Modem's firewall could block a stolen iPad from reporting home, without blocking internet usage for just about everything else. MobileMe is the *only* app that fails on my IOS stuff when the modem firewall is turned on. Huh.