Loosing field contents when positioned after file upload

I have a form that contains a file upload and a 2 text fields.

<li><%= t.file_field :artwork %></li>
<li><%= t.text_field :caption %></li>
<li><%= t.text_field :tags %></li>

When I submit the form with a file upload, and filling in the 2 other fields, the "caption" field drops from the posted fields.

Processing Admin::Campaigns::AdvertisementsController#create (for 127.0.0.1 at 2009-03-07 12:14:14) [POST]
  Parameters: {"campaign_advertisement"=>{"artwork"=>#<File:/var/folders/PD/PDwtDVH6G1qCmfQOwD-Og++++TI/-Tmp-/RackMultipart.15675.0>}, "tags" => "foo bar", "commit"=>"post", "campaign_id"=>"1", "authenticity_token"=>"Y0gwv6Ev9DdH4mgLAN86y+W+rMQOR2GsMoSqHKCdqoE="}

But if I submit the form without the file upload, the "caption" field comes through.

Processing Admin::Campaigns::AdvertisementsController#create (for 127.0.0.1 at 2009-03-07 12:17:37) [POST]
  Parameters: {"campaign_advertisement"=>{"artwork"=>nil, "caption"=>"asdfasdfasdf", "tags" => "foo bar"}, "commit"=>"post", "campaign_id"=>"1", "authenticity_token"=>"Y0gwv6Ev9DdH4mgLAN86y+W+rMQOR2GsMoSqHKCdqoE="}

I have no tricky javascript going on that would cause something like this. I'm running rails 2.3.0 rc1. I have tried rc2 but couldn't even get that working. (params wherent working, i.e. name="member[userame]" wasnt being turned into { :members =>{ :username => 'foo' }}.

I also noticed that If I switch the position of "tags" and "caption" around, so it reads:

<li><%= t.file_field :artwork %></li>
<li><%= t.text_field :tags %></li>
<li><%= t.text_field :caption %></li>

"tags" is now dropped from the posted fields. It would seem any field directly after the file upload is being dropped from post.