Re: RCBS RangeMaster 750
Did you try de-powering the unit and see if it will "reboot"? Disconnect the power supply and the battery. Sometimes works with other instruments. . .
Don't know if it would work with the 750 but it's worth a shot.
Overriding the calibration process is probably not a good thing anyway. You want accurate loads and there just may be a problem with the scale and its accuracy that's why you may be getting the message.
Hope that is not the case but good luck anyway!