I'm using the jQuery Form plugin, and I have a form that I am submitting using ajaxSubmit(). The server gives a JSON response to this ajax request. I have a file field on the form, but the server does not use the data from this field for this particular request. However, when the field is filled, the browser tries to download the JSON response as a file. When the field is empty, the browser correctly processes the JSON response.
What would cause the change in browser behavior? This happens in both IE8 and Firefox 3. The server response is identical for both cases, including headers. Content disposition is not set at all in the response headers.
