500 on network Graph

Created by: barockok

i got server error when request network graph page on one of my project, here my production log when that page was requsted

Started GET "/rt-baseapp/graph" for 116.66.206.172 at 2012-03-07 18:01:40 +0700
Processing by ProjectsController#graph as HTML
  Parameters: {"id"=>"rt-baseapp"}
  Rendered projects/graph.html.haml within layouts/project (2.6ms)
Completed 500 Internal Server Error in 730ms

ActionView::Template::Error (invalid byte sequence in UTF-8):
    2: %br
    3: #holder.graph.well
    4: 
    5: :javascript
    6:   var chunk1={commits:#{@commits_json}};
    7:   var days=#{@days_json};
    8:   initGraph();
  app/views/projects/graph.html.haml:5:in `_app_views_projects_graph_html_haml___431451517_101274720'

but i never get this error for my other project, i'm really new on ruby especially RoR, if it just something wrong with the configuration, please suggest me any sorry for my Bad English :D