I am not sure what is causing the error in your case. The error pretains to not having enough points for reference for the calibration VI. Instead, I would suggest building off one of the calibration examples built into LabVIEW. You mentioned you had installed LabVIEW 7.1, so the examples should be located in the following directory:
C:\Program Files\National Instruments\LabVIEW 7.1\examples\Vision\2. Functions\Calibration
I attached a couple of these for you to try. Use these as a template to build up your application. Sorry I didn't mention these last time. Hope they help you out!