I had to change my locate to a different one and after changing it back and reinstalling UTAU it was still like this and no voicebanks would make any sound nor I can type in kana. I have also included a screenshot. The files of the voicebanks are fine.
Could be that the installation file was downloaded before the locale change. When downloading the utau installer it can be corrupted when the locale isn't set before downloading it. to fix this you have to uninstall, delete the old install file and re download the installer.
Also make sure to change the installation location so you don't run into permission problems, anywhere outside of programfiles, like "my documents" will work.
Just as an extra note, once UTAU has been properly installed with Japanese locale, you can change your locale while UTAU is installed as long as you don't open it with a different locale. Your original post made it sound like perhaps you thought you needed to reinstall it any time you change your locale.
Otherwise, I'd check what HulderBulder said. You might just want to do a full clean sweep and fully redownload and install anew if it's been mojibake'd.