I'm getting the error below on clicking the main "Activity" link. I'm not at all familiar with ruby so would appreciate some suggestions as to the cause and possible solutions.

Processing ActivitiesController#index (for xxx.xxx.xxx.xxx at 2012-11-07 13:13:19) [GET]
  Parameters: {"action"=>"index", "id"=>"myproject", "controller"=>"activities"}
Rendering template within layouts/base
Rendering activities/index

ActionView::TemplateError (changes was supposed to be a Hash, but was a String) on line #9 of app/views/activities/index.html.erb:
6: <h3><%= format_activity_day(day) %></h3>
7: <dl>
8: <% @events_by_day[day].sort {|x,y| y.event_datetime <=> x.event_datetime }.each do |e| -%>
9:   <dt class="<%= e.event_type %>  <%= User.current.logged? && e.respond_to?(:event_author) && User.current == e.event_author ? 'me' : nil %>">
10:     <%= avatar(e.event_author, :size => "24") if e.respond_to?(:event_author) %>
11:   <span class="time"><%= format_time(e.event_datetime, false) %></span>
12:   <%= content_tag('span', h(e.project), :class => 'project') if @project.nil? || @project != e.project %>

    app/models/journal.rb:83:in `changes'
    app/models/issue.rb:41
    app/views/activities/index.html.erb:9
    app/views/activities/index.html.erb:8:in `each'
    app/views/activities/index.html.erb:8
    app/views/activities/index.html.erb:5:in `each'
    app/views/activities/index.html.erb:5
    passenger (3.0.15) lib/phusion_passenger/rack/request_handler.rb:96:in `process_request'
    passenger (3.0.15) lib/phusion_passenger/abstract_request_handler.rb:516:in `accept_and_process_next_request'
    passenger (3.0.15) lib/phusion_passenger/abstract_request_handler.rb:274:in `main_loop'
    passenger (3.0.15) lib/phusion_passenger/classic_rails/application_spawner.rb:321:in `start_request_handler'
    passenger (3.0.15) lib/phusion_passenger/classic_rails/application_spawner.rb:275:in `send'
    passenger (3.0.15) lib/phusion_passenger/classic_rails/application_spawner.rb:275:in `handle_spawn_application'
    passenger (3.0.15) lib/phusion_passenger/utils.rb:470:in `safe_fork'
    passenger (3.0.15) lib/phusion_passenger/classic_rails/application_spawner.rb:270:in `handle_spawn_application'
    passenger (3.0.15) lib/phusion_passenger/abstract_server.rb:357:in `__send__'
    passenger (3.0.15) lib/phusion_passenger/abstract_server.rb:357:in `server_main_loop'
    passenger (3.0.15) lib/phusion_passenger/abstract_server.rb:206:in `start_synchronously'
    passenger (3.0.15) lib/phusion_passenger/abstract_server.rb:180:in `start'
    passenger (3.0.15) lib/phusion_passenger/classic_rails/application_spawner.rb:149:in `start'
    passenger (3.0.15) lib/phusion_passenger/spawn_manager.rb:219:in `spawn_rails_application'
    passenger (3.0.15) lib/phusion_passenger/abstract_server_collection.rb:132:in `lookup_or_add'
    passenger (3.0.15) lib/phusion_passenger/spawn_manager.rb:214:in `spawn_rails_application'
    passenger (3.0.15) lib/phusion_passenger/abstract_server_collection.rb:82:in `synchronize'
    passenger (3.0.15) lib/phusion_passenger/abstract_server_collection.rb:79:in `synchronize'
    passenger (3.0.15) lib/phusion_passenger/spawn_manager.rb:213:in `spawn_rails_application'
    passenger (3.0.15) lib/phusion_passenger/spawn_manager.rb:132:in `spawn_application'
    passenger (3.0.15) lib/phusion_passenger/spawn_manager.rb:275:in `handle_spawn_application'
    passenger (3.0.15) lib/phusion_passenger/abstract_server.rb:357:in `__send__'
    passenger (3.0.15) lib/phusion_passenger/abstract_server.rb:357:in `server_main_loop'
    passenger (3.0.15) lib/phusion_passenger/abstract_server.rb:206:in `start_synchronously'
    passenger (3.0.15) helper-scripts/passenger-spawn-server:99

Rendering /usr/home/project/chiliproject/public/500.html (500 Internal Server Error)