I assume that the problem is NOT at your end.
It is either a firewall or an anti-virus program which is set to not allow certain attachments to pass through to the receivers end.
BTW, the last weeks there was a popular run for an Outlook 2002 extension called Extensio, this little program adds a tab to the OPTIONS section and allows or denies attachments to pass to Outlook 2002. If someone just installs the add-on, only the plain text comes through...the attachment file types need to be selected individually. Sounds very much like this filter is doing the job properly...check for that at your friends end.
Another reason for Linux...ahh well...SuSe 8.0 is running nicely here
