Hiki Error

invalid byte sequence in UTF-8 (ArgumentError)
/var/www/htdocs/rubygadgets/hiki/hiki/command.rb:65:in `initialize'
/var/www/htdocs/rubygadgets/ja/hiki.cgi:35:in `new'
/var/www/htdocs/rubygadgets/ja/hiki.cgi:35:in `block in <main>'
/var/www/htdocs/rubygadgets/hiki/hiki/storage.rb:13:in `open_db'
/var/www/htdocs/rubygadgets/ja/hiki.cgi:34:in `<main>'