wrong instance allocation (TypeError)

/usr/local/httpd/htdocs/mini/diary/tdiary.rb:895:in `open'
/usr/local/httpd/htdocs/mini/diary/tdiary.rb:895:in `do_eval_rhtml'
/usr/local/httpd/htdocs/mini/diary/tdiary.rb:890:in `do_eval_rhtml'
/usr/local/httpd/htdocs/mini/diary/tdiary.rb:854:in `eval_rhtml'
/usr/local/httpd/htdocs/mini/diary/index.rb:71