The interesting thing is that when using IE7 as an FTP Client to download these types of files from BulletProof FTP Server (or any FTP Server), the file will download correctly and will be stored in the user’s temporary directory on the local-os, then; prior, to executing the application which is associated with the document type, some other Microsoft process makes a security-determination on the file and decides to delete the file or not (without prompting the OS-User). This results in an error message to the User, indicating that the file could not be downloaded.

More Information from Microsoft is available at the following KB:
http://support.microsoft.com/kb/910274

PLEASE NOTE
While Microsoft’s Documentation and instructions on implementing the fix is correct, the Windows Registry Key for the fix is INCORRECT. In addition, Windows XP SP3 DOES NOT include a working HOTFIX (as they state).

Incorrect Registry Key
HKEY_CURRENT_USER\Software\Microsoft\Internet Explorer\Main\FeatureControl\FEATURE_PERMIT_CACHE_FOR_AUTHENTICATED_FTP_KB910274


Correct Registry Key
HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Internet Explorer\Main\FeatureControl\FEATURE_PERMIT_CACHE_FOR_AUTHENTICATED_FTP_KB910274