Problem with videos on heroku

Hi,
I have recently moved my RoR app on the Heroku platform, and almost
everything works fine apart from the videos. It works fine when my app
runs in local but not on heroku. This is the error log I'm getting, if
anyone knows where it can be coming from:

Processing VideosController#new (for IP at 2010-03-20 04:32:09) [GET]
  Session ID: 6abecf60c3369d7c7029e366bb801e08
  Parameters: {"artist_id"=>"10", "action"=>"new",
"controller"=>"admin/videos"}
Rendering within layouts/admin
Rendering admin/videos/new

ActionView::TemplateError (undefined method `video_file_relative_path'
for #<Video:0x2adc9839fe28>) on line #21 of app/views/admin/videos/
_form.rhtml:
18:
19: <p><label for="videos_image_file">Fichier Vidéo SWF</label><br/>
20: <% if @video.video_file %>
21: <%= link_to image_tag(url_for_file_column("video",
"video_file", :name => "thumbnail"))+"<br>", {:controller =>
url_for_file_column("video", "video_file")}, :popup => ['new_window',
'height=200,width=200'] %>
22: <% end %>
23: <%= file_column_field 'video', 'video_file' %>
24: &nbsp;&nbsp;&nbsp;

    #{RAILS_ROOT}/vendor/rails/activerecord/lib/active_record/base.rb:
1792:in `method_missing'
    #{RAILS_ROOT}/vendor/plugins/file_column/lib/file_column_helper.rb:
75:in `send'
    #{RAILS_ROOT}/vendor/plugins/file_column/lib/file_column_helper.rb:
75:in `url_for_file_column'
    #{RAILS_ROOT}/app/views/admin/videos/_form.rhtml:21:in
`_run_rhtml_admin_videos__form'
    #{RAILS_ROOT}/vendor/rails/actionpack/lib/action_view/base.rb:
314:in `send'
    #{RAILS_ROOT}/vendor/rails/actionpack/lib/action_view/base.rb:
314:in `compile_and_render_template'
    #{RAILS_ROOT}/vendor/rails/actionpack/lib/action_view/base.rb:
290:in `render_template'
    #{RAILS_ROOT}/vendor/rails/actionpack/lib/action_view/base.rb:
249:in `render_file'
    #{RAILS_ROOT}/vendor/rails/actionpack/lib/action_view/base.rb:
264:in `render'
    #{RAILS_ROOT}/vendor/rails/actionpack/lib/action_view/partials.rb:
59:in `render_partial'
    #{RAILS_ROOT}/vendor/rails/actionpack/lib/action_controller/
benchmarking.rb:33:in `benchmark'
    #{RAILS_ROOT}/vendor/rails/actionpack/lib/action_view/partials.rb:
58:in `render_partial'
    #{RAILS_ROOT}/vendor/rails/actionpack/lib/action_view/base.rb:
276:in `render'
    #{RAILS_ROOT}/app/views/admin/videos/new.rhtml:4:in
`_run_rhtml_admin_videos_new'
    #{RAILS_ROOT}/vendor/rails/actionpack/lib/action_view/base.rb:
314:in `send'
    #{RAILS_ROOT}/vendor/rails/actionpack/lib/action_view/base.rb:
314:in `compile_and_render_template'
    #{RAILS_ROOT}/vendor/rails/actionpack/lib/action_view/base.rb:
290:in `render_template'
    #{RAILS_ROOT}/vendor/rails/actionpack/lib/action_view/base.rb:
249:in `render_file'
    #{RAILS_ROOT}/vendor/rails/actionpack/lib/action_controller/
base.rb:699:in `render_file'
    #{RAILS_ROOT}/vendor/rails/actionpack/lib/action_controller/
base.rb:621:in `render_with_no_layout'
    #{RAILS_ROOT}/vendor/rails/actionpack/lib/action_controller/
layout.rb:243:in `render_without_benchmark'
    #{RAILS_ROOT}/vendor/rails/actionpack/lib/action_controller/
benchmarking.rb:53:in `render'
    /usr/local/lib/ruby/1.8/benchmark.rb:293:in `measure'
    #{RAILS_ROOT}/vendor/rails/actionpack/lib/action_controller/
benchmarking.rb:53:in `render'
    #{RAILS_ROOT}/vendor/rails/actionpack/lib/action_controller/
base.rb:911:in `perform_action_without_filters'
    #{RAILS_ROOT}/vendor/rails/actionpack/lib/action_controller/
filters.rb:368:in `perform_action_without_benchmark'
    #{RAILS_ROOT}/vendor/rails/actionpack/lib/action_controller/
benchmarking.rb:69:in `perform_action_without_rescue'
    /usr/local/lib/ruby/1.8/benchmark.rb:293:in `measure'
    #{RAILS_ROOT}/vendor/rails/actionpack/lib/action_controller/
benchmarking.rb:69:in `perform_action_without_rescue'
    #{RAILS_ROOT}/vendor/rails/actionpack/lib/action_controller/
rescue.rb:82:in `perform_action'
    #{RAILS_ROOT}/vendor/rails/actionpack/lib/action_controller/
base.rb:381:in `send'
    #{RAILS_ROOT}/vendor/rails/actionpack/lib/action_controller/
base.rb:381:in `process_without_filters'
    #{RAILS_ROOT}/vendor/rails/actionpack/lib/action_controller/
filters.rb:377:in `process_without_session_management_support'
    #{RAILS_ROOT}/vendor/rails/actionpack/lib/action_controller/
session_management.rb:117:in `process'
    #{RAILS_ROOT}/vendor/rails/railties/lib/dispatcher.rb:38:in
`dispatch'
    /usr/local/lib/ruby/gems/1.8/gems/thin-1.0.1/lib/rack/adapter/
rails.rb:60:in `serve_rails'
    /usr/local/lib/ruby/gems/1.8/gems/thin-1.0.1/lib/rack/adapter/
rails.rb:80:in `call'
    /home/heroku_rack/lib/static_assets.rb:9:in `call'
    /home/heroku_rack/lib/last_access.rb:25:in `call'
    /usr/local/lib/ruby/gems/1.8/gems/rack-1.0.1/lib/rack/urlmap.rb:
46:in `call'
    /usr/local/lib/ruby/gems/1.8/gems/rack-1.0.1/lib/rack/urlmap.rb:
40:in `each'
    /usr/local/lib/ruby/gems/1.8/gems/rack-1.0.1/lib/rack/urlmap.rb:
40:in `call'
    /home/heroku_rack/lib/date_header.rb:14:in `call'
    /usr/local/lib/ruby/gems/1.8/gems/rack-1.0.1/lib/rack/builder.rb:
60:in `call'
    /usr/local/lib/ruby/gems/1.8/gems/thin-1.0.1/lib/thin/
connection.rb:80:in `pre_process'
    /usr/local/lib/ruby/gems/1.8/gems/thin-1.0.1/lib/thin/
connection.rb:78:in `catch'
    /usr/local/lib/ruby/gems/1.8/gems/thin-1.0.1/lib/thin/
connection.rb:78:in `pre_process'
    /usr/local/lib/ruby/gems/1.8/gems/thin-1.0.1/lib/thin/
connection.rb:57:in `process'
    /usr/local/lib/ruby/gems/1.8/gems/thin-1.0.1/lib/thin/
connection.rb:42:in `receive_data'
    /usr/local/lib/ruby/gems/1.8/gems/eventmachine-0.12.6/lib/
eventmachine.rb:240:in `run_machine'
    /usr/local/lib/ruby/gems/1.8/gems/eventmachine-0.12.6/lib/
eventmachine.rb:240:in `run'
    /usr/local/lib/ruby/gems/1.8/gems/thin-1.0.1/lib/thin/backends/
base.rb:57:in `start'
    /usr/local/lib/ruby/gems/1.8/gems/thin-1.0.1/lib/thin/server.rb:
150:in `start'
    /usr/local/lib/ruby/gems/1.8/gems/thin-1.0.1/lib/thin/controllers/
controller.rb:80:in `start'
    /usr/local/lib/ruby/gems/1.8/gems/thin-1.0.1/lib/thin/runner.rb:
173:in `send'
    /usr/local/lib/ruby/gems/1.8/gems/thin-1.0.1/lib/thin/runner.rb:
173:in `run_command'
    /usr/local/lib/ruby/gems/1.8/gems/thin-1.0.1/lib/thin/runner.rb:
139:in `run!'
    /usr/local/lib/ruby/gems/1.8/gems/thin-1.0.1/bin/thin:6
    /usr/local/bin/thin:20:in `load'
    /usr/local/bin/thin:20

Thanks,

Roch