I use Runkeeper as my cycling app on my iPhone 4. My daughter has it on her iPhone 4S, but her mileage is always about 30% high. We've uninstalled and reinstalled the app and also powered the phone off and back on to no avail. The time is good, only the mileage is off and she says the GPS seems to function fine in other, non-fitness applications. Anyone else? Anyone have an idea of how to fix it?