I have a strange problem.
I have an iPad with iOS 5.0.1 (9A405) and iOS SDK 5.0.1 with Xcode 4.2 (Build 4C199) installed on my Mac.
Xcode doesn't see my device. It says "iOS Device" not "Sauron's iPad" as usual.
(I am sure that device is connected because I see it in iTunes.)
Xcode denies to start my application on device.
"Xcode cannot run using selected device. No provisioned iOS devices
are available with a compatible iOS version. Connect an iOS device
with a recent enough version of iOS to run your application or choose
an iOS simulator as the destination."
Select Organiser from Xcode. Now under Devices, select your device. If it is not ready for development then click use for development.
If above doesn't solve your problem then from your project settings, set deployment target to one which your app is developed for or lesser.
Otherwise there is some issue with certificates and provisioning profiles. Make sure your device's UDID is added in the provisioning profile you are using.