If you updated your Remote Desktop client software to version 2.1 but still have the Remote Desktop 2.0 admin application on the same computer, the admin application won't launch when you try to open it. Instead, it will start an installation routine and display the message, "A newer version of the package is already installed."
When you click Done to close this message, the application unexpectedly quits.
This usually happens if you moved Remote Desktop from the default Applications folder (/Applications) to another location. Here's why:
If you have Remote Desktop 2.0 on your computer, Software Update will offer you one of two versions of the 2.1 update: Remote Desktop Admin Update 2.1 or Remote Desktop Client Update 2.1. It will offer you the Admin version if the Remote Desktop application is in the Applications folder, or the Client version if it's not in there. The latter case leads to a mismatch of your client and admin software, which will prevent the Remote Desktop admin application from launching.
To resolve the issue, put the Remote Desktop application back in the Applications folder. Choose Software Update from the Apple menu, and this time it will offer you the Admin update. Install it, and you're done.
Tip: The Admin update includes the Client update, but not vice versa. If you get the Admin update first, everything will get updated at once.