Please Note: These instructions assume you’re using Ubuntu (or any other version of Debian). If you’re not, these instructions may differ.
Open /etc/locale.gen in your favorite editor, and fine this line:
# en_US.UTF-8 UTF-8
and change it to this
en_US.UTF-8 UTF-8
Then run dpkg-reconfigure locales.
Finally, run update-locale LANG=en_US.UTF-8, and restart your system. I would recommend running these instructions on a fresh install to guarantee that there will be no issues.
If these don’t help I would ask you to post a full stack trace like @clarkej said.