The +FHNG status string from the modem indicates that the modem
firmware encountered some problem--there is no way for the fax
software to recover from this as the line has already been hung
up. These types of errors typically indicate a firmware problem,
though in this case the status code is very odd. The only thing I
can possible think to check is whether or not the order of bits
sent to the modem is correct. The probemodem result indicates that
the modem understands the +FBOR command, so there should be no
problem.
I would try other fax machines to see if the problem is repeatable.