Internet Explorer file downloads over SSL do not work with the cache control headers

When you try to open a Microsoft Office document or a PDF file by typing an HTTPS URL for the document in the Address bar of Internet Explorer 6 Service Pack 1 (SP1), you may receive the following error message:

Unable to download.

Internet Explorer was unable to open this site. The requested site is either unavailable or cannot be found. Please try again later. 

 

This issue occurs if the server sends a "Cache-control:no-store" header or sends a "Cache-control:no-cache" header.

 

http://support.microsoft.com/kb/323308