Attachments disappear when I open Outlook

[Trevor]

I am using Vista Ultimate SP1 and Office Professional 2007 (both fully up to
date) and am having a problem with Outlook and some attachments.

What is happens is that wjen the mail is downloaded in Outlook I can see the
attachment gem clip with the message. However, when I double click the
message there is no attachment and the gem clip has disappeared.

How do I fix this problem?

Thanks

Trevor