Unable to resolve target 'android-X' until the SDK is loaded
If you find this cryptic error in your Eclipse while working with a new cloned project, you must update your SDK through Android SDK Manager and install ADT's last version through Eclipse update.
Note: in "Preferences window > Android" appears a more clear message.
This Android SDK requires Android Developer Toolkit version 22.0.0 or above. Current version is 21.0.1.v201212060256-543035. Please update ADT to the latest version.