Paul Tugwell wrote:

A customer of mine sometime gets the error message 'The operation
failed' when opening an attachment. This has been seen for .xls and
.zip files from a particular source. If outlook is closed then
re-opened, the attachment opens fine. Also, if the same file is sent
again, the copy will open.

Possibly a Secure Outlook Temp Folder issue. See
http://www.howto-outlook.com/faq/securetemp.htm
--
Brian Tillman