This is not necessarily a Game Breaking Bug for the NEW UI as a whole, but rather something specific to your machine. We will keep an eye open for similar reports, but so far it's the only report with that issue. As for general troubleshooting, make sure you've checked out the sticky thread in the support section. As a way to try and quickly resolve the issue you can open the launcher and then click 'options' then 'Validate Installation'. If that still does not work, you can uninstall the game and then reinstall using the directions in the first post. If you do reinstall, make sure you open the launcher as administrator and try disabling your antivirus during the download and installation process.
If that fails, you can revert to the old UI to get back playing immediately.