CabLib Extract ERROR when converting InfoPath files

When converting Infopath forms, in some environments you may see the following error in documentconverter.log or in the Windows Application Event Log.

"CabLib Extract ERROR while extracting files from cabinet stream: The file is not a cabinet"

The reason for this error is that the XSN file associated with the XML file cannot be retrieved by the Conversion Service. Instead a different HTML page is returned which is not a valid XSN file.

This may be due to:

1. Forms authentication is used on the Web Application hosting the XSN file. Please enable Windows Authentication as well.

2. A (transparent) proxy server is used in the environment that intercepts all HTTP calls. Please make sure that the account the Conversion Service runs under is recognised by this proxy server.