Assume that you have one or more language packs installed on a Windows RT device, and then you upgrade the device to Windows 8.1 RT Preview. In this situation, you cannot install language packs after the upgrade.
Note When you install Windows RT 8.1 Preview, all the language packs that you installed are removed. Only the base language is preserved. This is an expected behavior.
An update (2865138) is available to resolve this issue. This update is installed when you upgrade to Windows RT 8.1 Preview.
Note If this issue already occurs, upgrade to the release version of Windows RT 8.1 when it becomes available.
Microsoft has confirmed that this is a problem in the Microsoft products that are listed in the "Applies to" section.
For more information about software update terminology, click the following article number to view the article in the Microsoft Knowledge Base:
824684 Description of the standard terminology that is used to describe Microsoft software updates