ASP FORM POST Confliting query string acl,policy

I need a little help with a form in ASP .NET C# – it's a standard web application.

The form is used to upload file to Amazon S3 through Cloudfront

<form name="form" action="http://ift.tt/1FF8cdd" method="post" enctype="multipart/form-data">

I tryed to use the HTML submit button inside the form, but it just reloads the page.

<input type="submit" name="submit" value="Upload to Amazon S3" />

So I used a ASP button with PostBackUrl to Cloudfront.

<asp:Button ID="Button1" runat="server" Text="Upload to Amazon" PostBackUrl="http://ift.tt/1FF8cdd" />

When I submit with the ASP button, the cloudfront xml returns an error:

Conflicting query string parameters: acl, policy

I didn't find anything useful on the internet about it.

This same form works just fine in PHP.

This is the form structure:

<form name="form" action="http://ift.tt/1FF8cdd" method="post" enctype="multipart/form-data">
                Key to upload: 
                    <input type="input"   name="key" value="Test/${filename}" /><br />
                    <input type="hidden" name="acl" value="public-read" />
                    <input type="hidden" name="success_action_redirect"
                           value="http://ift.tt/1IyiJKW"/>
                content-type: 
                    <input type="input"   name="content-type" value="binary/octet-stream" /><br />
                    <input type="hidden" name="x-amz-meta-uuid" value="14365123651274" />
                    <input type="text"   name="x-amz-credential" 
                           value="AKIAEXAMPLE/20150415/eu-west1/s3/aws4_request" />
                    <input type="text"   name="x-amz-algorithm" value="AWS4-HMAC-SHA256" />
                    <input type="text"   name="x-amz-date" value="20150415T000000Z" />

                Tags for File: 
                    <input type="input"   name="x-amz-meta-tag" value="" /><br />
                    <input type="hidden" name="policy" value="<The policy encoded in Base 64>" />
                    <input type="hidden" name="x-amz-signature" value="<The encoded signature>" />
                File: 
                    <input type="file"   name="file" /> <br /></form> 

And this the policy:

{ "expiration": "2015-04-15T12:00:00.000Z",
"conditions": [
{"bucket": "mybucket"},
["starts-with", "$key", "Test/"],
{"acl": "public-read"},
{"success_action_redirect": "http://ift.tt/1IyiJKW"},
["starts-with", "$Content-Type", "binary/"],
{"x-amz-meta-uuid": "14365123651274"},
["starts-with", "$x-amz-meta-tag", ""],
{"x-amz-credential": "AKIAEXAMPLE/20150415/eu-west-1/s3/aws4_request"},
{"x-amz-algorithm": "AWS4-HMAC-SHA256"},
{"x-amz-date": "20150415T000000Z" }
]
}