Xcode consistently fails to launch app on device: "Unknown packet reply: "timeout" to environment packet."

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 o开发者_如何转开发r rebooting the development machine. Cleaning and recompiling also does not fix the problem.

It's not limited to the project; once it happens I can no longer launch any apps through Xcode.

The device is an iPad running iOS 4.3.5; the development machine is a Macbook running Lion.

Haven't see similar reports. I would suspect the usb cable at this point.

I still have no idea what was causing this before, but I haven't seen it since upgrading to Mountain Lion and Xcode 4.4.1 so I'm answering the question to mark it closed.