Two of my customers are receiving the above message. The form works flawless for 30+ other customers, including myself.
The form is posted in a document library on a SharePoint site. The error occurs after the customer has clicked 'Submit' on one specific InfoPath form.
The InfoPath form template Submit Options are as follows: "Allow users to submit this form" is checked. Send form data to a single destination is not. The submit type is managed by the "Perform custom action using Rules" The rule has an action of "Submit using a data connection". The data connection wizard shows the e-mail To: Cc: etc, The 'Select the attachments to include with the e-mail message.' is set to "Send the form data as an attachment" with the attachment name being one of the form's fields + Date1 (to ensure unique file naming) . The 'Attach the form template to ensure that users can open the form' is NOT checked. It previously was, but during my diagnostics of this problem, I've turned that off.
Since this problem is isolated to two users, I'm assuming it is a user profile folders for either InfoPath or Outlook.