Fax with cover page or inline data

Hi, if I send something to the fax printer that consists of only an
attachment, it works fine. If I go into the fax console, start a fax, and
add an attachment, it works fine. However, if I try and add a cover page or
add text in the box at the bottom, I get errors such as "The data is
Invalid" (text at the bottom) and "A StartDocPrinter call was not issued"
(cover page). Anyone have any ideas? I'm running Windows 7 SP1 Ultimate
64 bit.