I've tried that, didn't work.
It's a stand alone pc & the only one I have that's set to take updates from MS automatically, so all I can think of is it's either a duff update or the fax modem itself is cream crackered. I suppose I can try a new modem card for a few quid. The fax service itself says it's tickety boo, all ok in device manager, nothing in the event viewer & the line is ok - we use it as a phone/fax, so we know that's not it.
Seems a bit extreme to go for a rebuild to fix this.