Sorry if this reply is late, I just read it today 11-19-08.
I also use Mastercam (X3) and CIMCO Edit (ver 5.12.06) to run my Conquest 42. I'm connected to the lathe RS-232 from my laptop PCMCIA port which uses a Quatech card and drivers.
My DNC settings in CIMCO are
stop bit: 2
baud rate: 9600
data bits: 7
All other DNC settings in CIMCO were left as default.