Part of the problem was on the adapter board on which the rabbit connector was mounted. After fixing this, 10.72C on the Windows 10 machine did compile and save the program in flash. However, it would not start debug execution. It was hung trying to communicate with the target.
To isolate the problem different programming cables and a number of RCM6700's were tried. Nothing helped.
Finally, 10.72C was uninstalled and reinstalled (using typical install). After setting the project options again, it does now have debug control. It looks like the Windows 10 upgrade caused some problem with the installed 10.72C software.