a bit more info would help
what os
what antivirus do you have is it disabled....firewalls turned off
networkcard setup correctly
static ip
10baset_halfduplex
image trying to flash
what box
how many chips
what error messages do you get
etc etc
then we may be able to help.
by the way its called a nullmodem cable.
Nope you dont want the "incoming connection" no need for that.
Just plug in the null modem cable into the back of your PC, and into the back of your DBOX.
Then attach (as well as the nullmodem) a crossover ethernet cable to the PC and DBOX. You need to set the ethernet connection to use a STATIC IP - such as 192.168.0.2.