Installing Fax Device Results In Getting The Error?

we installed the Microsoft Fax process on an XP Pro PC. It is setup only to send faxes and works great most of the time. However, every once in awhile, it will stop sending faxes even though there are faxes still showing in the Outbox of the Fax Console and Fax Monitor shows Ready to send. What we do see in the Fax Monitor's more>> window is that the last fax said that the fax did not answer, fax was cancelled after about 5 minutes of sitting there trying and it requeued the fax. It then shows a message of Fax Device Error.There is nothing in the Event Logs showing that there is a device problem. Looking at the Printers and Faxes in the Control Panel show the Fax is Ready.