Try resetting your Encore preferences.
See "Recreate the Adobe Encore Preferences File" in this link for windows:
http://helpx.adobe.com/encore/kb/troubleshoot-damaged-projects-encore- windows.html
This problem may require resetting workspaces. Note in the abov e link that that requires manually resetting the preferences. But try the easy fix first!
Please let us know if this works.
For Mac, see "Re-create Preferences File" here:
http://helpx.adobe.com/x-productkb/global/troubleshoot-system-errors-f reezes-mac.html