If your Mac OS X 10.3 computer has been in sleep mode at any time since the last restart, the computer may not accept incoming faxes. This document applies to Mac OS X 10.3 through 10.3.9.
To resolve this issue, either restart the computer before you intend to receive a fax, or use the Energy Saver preference pane to disable sleep.
If you see the message "there was a software fax error," see this document.