I am writing an iPad app and I would like to use Xcode Instruments to see if my app has any memory leaks. I have used Instruments successfully before but with Xcode 4.0.2 recen
Have you tried changing the profile build from Release to Debug (go into "Edit Schemes" and you can change it there for Profiling)?
It could be something in the release build is causing Instruments to disconnect.
Also, pull up the device console in Organizer while it is running, and see if you see any messages related to the detachment.
Be sure, you device is turned on (in some cases it can be spontaneously shut down).