I encountered this as well. As Cristiano says, see SAP note 1960137. In my case, I wanted to update one of my folders, so I had to manually add "Master Locale" to the folder, following these steps:
Go to the PCD Inspector (System Administration --> Support --> PCD Inspector). Click the "I Accept" button
Browse to the folder you want to update, then click "Prop Editor"
Click the icon in the upper right that looks like a large "P" with an asterisks next to it.
Enter this in the Property ID field: com.sap.portal.pcd.unit.OriginalLocale
Enter this in the Property Value field: en (in my case, English, but enter the language you want)
Choose "LOCALE" from the Property Type drop-down box
Click the "Create" button