Fax Mail Transport error

Im on Windows XP SP2 using Microsoft Office 2003 and Windows XP Fax. I open up a template in Word to send a test fax to ourselves and merge to email. To: Fax, Mail Format: Attachment. It goes to the outbox in Outlook just fine. When I go to send/receive, I receive this error message as an email in my inbox

Your message did not reach some or all of the intended recipients.

Subject:
Sent: 2/16/2007 11:11 AM

The following recipient(s) could not be reached:

'xxx-xxx-xxxx' on 2/16/2007 11:16 AM
The Microsoft Fax transport failed to deliver the message to the recipient.
The message body cannot be printed.

*xxx-xxx-xxxx being our number

This process use to work on 3 computers and now 2 computers give this error (happened to the two computers at different times), while one still works. This may be too vague but have you seen any problems of this nature?
We use this feature to send out many faxes so we do not have to do it manually.