Bad news for those iphone developers that are yet using Snow Leopard with Xcode 4.2
Since I've updated my iPhone to iOS 5.1, Xcode 4.2 doesn't recognize my iPhone anymore.
I seems that if you want to develop for the new releases of iOS you have to install Xcode 4.3 on Mac OS X Lion, anyway there is a workaround to continue using Mac OS X Snow Leopard and Xcode 4.2, simply run the following steps:
1. Download Xcode 4.3.1 from the developer site
2. Mount the downloaded DMG file
3. Inside the mounted disk right click on the Xcode icon and select "Show Package Contents"
4. Goto the Contents/Developer/Platforms/iPhoneOS.platform/DeviceSupport directory
5. Copy the /Applications/Xcode.app/Contents/Developer/Platforms/iPhoneOS.platform/DeviceSupport/5.1 (9B176) directory into the Xcode 4.2 (should be /Developer/Platforms/iPhoneOS.platform/DeviceSupport)
6. Goto the Contents/Developer/Platforms/iPhoneOS.platform/
7. Copy the "version.plist" file into the Xcode 4.2 app (should be /Developer/Platforms/iPhoneOS.platform/)
8. Restart Xcode 4.2 and connect your iPhone.
All should work fine.