form_for vs remote_form_for

I currently have this form:

<% form_for :workout_file, :url => { :action => 'create' }, :html => { :multipart => true } do |f| -%>   <p><%= f.file_field :uploaded_data %></p>   <p><%= submit_tag :Create %></p> <% end -%>

At the end of the action create I've got:

render :partial => 'workouts'

I'd like the partial to render inside a specific div, so I change the form tag to:

<% remote_form_for :workout_file, :update => 'contentArea', :url => { :action => 'create' }, :html => { :multipart => true } do |f| -%>

But that creates the following error from attachments_fu:

Thanx in advance!!

NoMethodError in WorkoutController#create

undefined method `content_type' for "/files/apps/polar/ 07031301.hrm":String

RAILS_ROOT: script/../config/.. Application Trace | Framework Trace | Full Trace

vendor/plugins/acts_as_attachment/lib/technoweenie/acts_as_attachment/ instance_methods.rb:56:in `uploaded_data=' /usr/lib/ruby/gems/1.8/gems/activerecord-1.15.1/lib/active_record/ base.rb:1660:in `attributes=' /usr/lib/ruby/gems/1.8/gems/activerecord-1.15.1/lib/active_record/ base.rb:1659:in `attributes=' /usr/lib/ruby/gems/1.8/gems/activerecord-1.15.1/lib/active_record/ base.rb:1493:in `initialize_without_callbacks' /usr/lib/ruby/gems/1.8/gems/activerecord-1.15.1/lib/active_record/ callbacks.rb:225:in `initialize' /usr/lib/ruby/gems/1.8/gems/activerecord-1.15.1/lib/active_record/ validations.rb:726:in `create!' app/controllers/workout_controller.rb:94:in `create'