Hiki Error

invalid byte sequence in UTF-8 (ArgumentError)
/home/sakai/www/hiki-github/hiki/command.rb:65:in `initialize'
/home/sakai/www/hiki-github/hiki.cgi:35:in `new'
/home/sakai/www/hiki-github/hiki.cgi:35:in `block in <top (required)>'
/home/sakai/www/hiki-github/hiki/storage.rb:13:in `open_db'
/home/sakai/www/hiki-github/hiki.cgi:34:in `<top (required)>'
/var/www/msakai.jp/hiki/hiki.cgi:10:in `load'
/var/www/msakai.jp/hiki/hiki.cgi:10:in `<main>'