Outlook attachments are unavailable with the AntiVirus Outlook plug-in installed and enabled.
You attempt to open an attachment and nothing happens.
Early builds of Microsoft Outlook have been updated to resolve API issues.
Update Outlook and/or the Microsoft Office suite to the latest version to resolve the issue.
As a workaround you can disable the AntiVirus Outlook plug-in. The location will vary depending on which Office suite you are using.
In Office XP: