$20 the reason you can't start blockland is because you don't have any data. Install blockland.
... You don't understandI installed Mac OS X Lion on a 2TB External Hard-Drive, then downloaded Mountain Lion from the App Store and installed that. After I downloaded BlocklandLauncher so I could re-download the content and play, but the error shown in the OP has appeared.
You need to install Blockland. BlocklandLauncher is the game's launcher, not the installer.