When you select another language (French, Japanese, etc.) on login page, and after the connection, the browser still white.

To find the issue, you can try this tasks:

Open the CloudStack Web UI with a browser which include "Developer Tools" (Chrome / IE / Firefox-FireBug)

After the click:

We can check directly on messages_XX.properties (here Japanese)

Oh, three bad lines with \n.

Jump to Transifex Client UI project

You can fix the bad strings (use KEY: xxxxx to filter)

Remove the newline, and click on Save button.

After, the final step is to update CloudStack branch (or master) with the resources files from transifex.
To do this: Ask to a CloudStack committee to perform this instructions: Update L10N files from Transifex to git repo