Further search on this forum has shown 2 recent similar issues. Nobody has posted a fix. The fault first noticed on the 13th April and was not apparent on the 11th. The only apparent change was an update to MS Office 2003 which was installed around that time. Chrome "is up to date", Windows 7.
Attachment is an example of what is downloaded when an attachment is clicked - OOPS it won't allow this I get this message : "The uploaded file Downloader (43) of type application/octet-stream is not allowed"