Not easily deterred by this kind of things particularly the downloaded file was a text file and that I was very knowledgeable in QIF file format, I opened the file in a text edit and the reason was so obvious.
What happened was that at the end of the download of the correctly structured QIF data, their .Net web server application must have thrown an exception and their application then formatted the message into HTML format ramming it into the QIF file. Here is the error message:
Not very nice. I doubt the download feature was used much otherwise people would have complained or people just believing mistakenly that the Internet corrupted the download.
Server Error in '/Client' Application.
Runtime ErrorDescription: An application error occurred on the server. The current custom error settings for this application prevent the details of the application error from being viewed remotely (for security reasons). It could, however, be viewed by browsers running on the local server machine.
Details: To enable the details of this specific error message to be viewable on remote machines, please create a <customerrors> tag within a "web.config" configuration file located in the root directory of the current web application. This
tag should then have its "mode" attribute set to "Off".<!-- Web.Config Configuration File -->
Notes: The current error page you are seeing can be replaced by a custom error page by modifying the "defaultRedirect" attribute of the application's <customerrors> configuration tag to point to a custom error page URL.<!-- Web.Config Configuration File -->
<customerrors mode="RemoteOnly" defaultredirect="mycustompage.htm">
Once I deleted the error message from the QIF file, I could import it successfully. Have they actually tested their web application at all? I wonder!