Internet Explorer uploading file data as a String in Rails 2.3.4

Some random IE users (versions 6-8) aren't able to upload files. The data that comes in the POST is a String instead of a File object.

Has anyone seen this and have any insight into where the issue may be?

Valid upload:

attachment_data: #<File:/tmp/RackMultipart7719-0>

Invalid upload:

attachment_data: "Soccer profile.doc"

[UPDATE]

Some random IE users refers to 5 or 6 out of thousands. So, yes it's a multipart form. And it is already using Paperclip开发者_Go百科.

Do you have :multipart => true in the form_for?