I have 5 devices under MobileMe''s Find My iPhone. After iOS 4.2.1, FMi can't find all the devices. This is what I do to enable the feature AGAIN 1) Go into MAPS app. Search for your current location. A pop-up message will appear asking you to allow location search. Tab YES. 2) Go into SETTINGS>GENERAL>MAIL, CONTACTS, CALENDARS>MOBILEME. 3) Turn Find My iPhone/iPad OFF. Click DONE if applicable. 4) Re-enable the FMi again by clicking the feature to ON again. *note: Step 1 is needed if you have just upgraded and have not accessed the MAPS app yet. Retest the result using the FMi app. It should work. I notice my iDevices prompted me to check my Me.com account settings again. Eventhough MYi feature is turned on, the server doesn't seem to register that. I rebooted devices to no avail. But tried the above steps and it solved the problems.