Problem with file uploads

I'm trying to write a simple file upload form. The upload form is a
view like this:

<%= start_form_tag( { :action=>'upload' }, :multipart => true) %>
<p>Upload File: </p>
<%= file_field('upfile', 'data') %>
<%= submit_tag('Upload') %>
<%= end_form_tag %>

The controller has upload defined, and there is an upload.rhtml file in
the correct spot. However Post attempts to the upload action fail with
a 404 error. The strange thing is, GET works perfectly fine (the 500
error is due to a list in the upload view being undefined due to the
lack of expected POST data). Here are the results of a submission of
my form, followed by the results of a direct browser access.

"POST /connect/upload HTTP/1.1" 404 291
"GET /connect/upload HTTP/1.1" 500 7688

Anyone have any ideas why this may be happening? I'm using rails 1.1.6
with Ruby 1.8.4, on a CENTOS 4.3 (Fedora Clone) box.