Ok, let's handle this one issue at a time. Computers must be slow, 486-25sx is the fastest I even had luck with using the Spectra software, the program must be run under DOS natively, with enough memory, not under a DOS box in windows, and the computer must have a real serial port, no USB adapter. That said, if you have programmed other Spectra radios with this setup before, including your RIB (check the batteries and or power cable) to radio cable I would look at rear connector of the newer radio first. Does the newer radio work properly, all the buttons work, and you can key up and get power and receive? If not check the 15 pin cable to make sure the EMERGENCY line is properly connected. I have seen some radios that lock up if that line is no properly hooked up. BTW they may or may not program either.
Have you tried to verify that you are using the correct serial port by running the test F-6 in the setup menu. Does the radio flash PROGRAMMING when it tries? If you get a confirmation that you have the right port, and the radio does flash PROG, but still fails. I would look at the computer speed, but you have to get to this point first.