Trying to create a external contenttype by using the Microsoft SharePoint 2010 Designer I got the error “The Business Data Connectivity Metadata Store is currently unavailable”
This was caused by the fact that I had installed a “PowerPivot” SharePoint 2010 installation and during the installation you do not run the SharePoint 2010 Configuration Wizard.
First ensure all update are installed, by using Microsoft Windows Update, then go to the Microsoft SharePoint 2010 Central Administration page and click on Configuration Wizards:
Run the wizard, make sure the Business Data Connectivity Service is checked.
After running this wizard I still got the same exception, this was caused by some services where not running, check if all services are running: Central Administration > Manage services on server:
After starting some services, see screendump the error was resolved.