Ken, I think the link below will answer your question. I've run into this before too...
http://support.microsoft.com/support/kb/articles/q197/7/46.asp
6:22 pm EST Update: here's another link too:
http://support.microsoft.com/support/kb/articles/q236/4/32.asp
http://support.microsoft.com/support/kb/articles/q235/8/70.asp

Note, I've also run into this when security settings prevent programmatically sending attachments through Outlook too. You should check those settings against a system that works correctly. I used to have a list of the settings to change, but I can't locate it. Maybe someone else has run into this too and will answer your thread. In the meantime, I'll keep looking for my old notes on this.

Tracy

>I have encountered a strange behavior when sending an e-mail with attachments added with the attachments.add() method. The Attached files show up in the message as icons in outlook or as filenames in a text based email system. I have not been able to find any documentation on this behavior. Do you know what may cause this to happen? When I send a email where a file was attached through the Outlook interface the attachments show in the attachment window below the below the body.
> I would appreciate any information on having the attachments show up in the attachment window when added with the Attachments.add() method.