Xcode始终未能在设备上启动app:“未知包应答:环境包超时”。

Since upgrading to Xcode 4.2 I've regularly encountered an error where attempting to debug an app fails with the message "Unknown packet reply: "timeout" to environment packet." Restarting the device does not consistently solve the problem (though it sometimes does), nor does restarting Xcode or rebooting the development machine. Cleaning and recompiling also does not fix the problem.Since upgrading to Xcode 4.2 I've regularly enc