I'm having a bit of an issue testing my app using my iPhone. Last week I upgraded to Xcode 4.3. I was able to test my apps on my iPhone (which was running iOS 4.3). Today I upgraded my iPhone to iOS 5.1 and now Xcode wont detect my iPhone (btw SDK is 5.1).
I'm not too sure what to do, I've even tried changing the Deployment target in Xcode back down to 4.3, but still nothing.
Make sure the device is "Enabled for development" under Organizer in Xcode. I've seen cases, where Xcode doesn't recognise the device, because it wasn't setup to be a development device.