Unable to attach files to ClearQuest record via OSLC

I am trying to add attachments to a record after performing a creationDialog through a .NET WebBrowser control.  The cause for this solution is that the ClearQuest Web attachments tab fails when inside of the WebBrowser control.  So my workaround will be to use the OSLC API to post the attachments after the record is saved.  I am performing this using a HttpWebRequest in .NET 4.0.

However, I am receiving this error when trying to POST attachments:

<Error xmlns="http://open-services.net/xmlns/cm/1.0/" xmlns:cq="http://www.ibm.com/xmlns/prod/rational/clearquest/1.0/" xmlns:rdf="http://www.w3.org/1999/02/22-rdf-syntax-ns#">
  <message>CRRCM9964E: Attachments were not specified while posting to the Attachment context.</message>
  <statusCode>400</statusCode>
</Error>

POST http://...:.../cqweb/oslc/repo/.../db/.../record/...-.../field/Attachments/attachment
Accept: application/xml
Content-Type: multipart/form-data; boundary=MimeSection
Content-Length: 398


--MimeSection
Content-Disposition: form-data; name="description"
Content-Type: text/plain; charset=US-ASCII
Content-Transfer-Encoding: 8bit 

Test Description
--MimeSection
Content-Disposition: form-data; name="file"; filename="test.txt"
Content-Type: application/octet-stream; charset=ISO-8859-1
Content-Transfer-Encoding: binary

this is a test attachment file.
--MimeSection--