If you have an iOS 5 device that is configured to use iOS 5′s new WiFi sync feature, and you’re experiencing high CPU when using Xcode or it becomes non-responsive¬†(eg. Xcode gets pegged at 100% or higher for not apparent reason on an otherwise idle machine), disable WiFi sync. Once I disabled WiFi sync, the high CPU usage went away. I’m guessing that perhaps my older version of Xcode (3.2.6) is trying to sync with the device over WiFi but doesn’t quite know how to do that.