If you receive:
InfoPath cannot open the following form: <url>
The file is not a valid XML document.
DTD is prohibited.
This problem occurs when the form template that was used to create the form is not available or cannot be downloaded from the site. The form template was not sent in the e-mail message, or the form template was not published to a shared location.
The resolution is to add the URL for the form template to your trusted sites or local zone and ensure that the person has ‘Contribute’, the minimum permissions required to update InfoPath forms.
Thanks for sharing nice info!
I have the same problem when working inside the server box. But I tried this on a client computer and it’s working fine. I’ve checked IE versions on server and client are same Version 9. Had tried both 32 and 64 bit of IE on the server.
When working on the server box, you’ll get this message because the download is blocked thanks to the loopback check. Try disabling the loopback on the server if you want to work directly on the server (obviously don’t do this for production). Here is the link to disable the loop back check: http://iedaddy.com/2009/04/sharepointdisable-loopback-check/