Not all attachments can be rendered

Outlook 2000 - 2003 is having problem with the Fax Transport.

1.)When attepmting to send a fax, on the 2003 client, a delivery failure is
recieved immediatley with "The Microsoft Fax transport failed to deliver the
message to the recipient. Not all attachments can be rendered."
The attachment is a PDF and the user is using a Vcard.

2.) When attepmting to send a fax, on the 2000 client, it hangs in the
outbox. Attachment is a Word document and no signature is used.

Environment is Server 2003 Standard, Exchange 2003, Windows XPP SP2.

Thanks in advance;