vista business-windows fax will not receive automatically

i'm running vista business. windows fax and scan will not receive faxes
automatically, even though i have the auto recieve box checked.

all that happens is that i hear the ringing, and the fax staus window
says "ringing".

i've tried changing the number of rings, but that does nothing.

windows defender firewall is on, but windows fax and scan is set as an
exception. i can recieve faxes if i manually answer the call.

i checked the microsoft kb, but that says nothing about this.

does anyone have a fix?

thanks,

m ades