The header info in the reference files for the step-wedge images included in QTR isn't recognized in ColorPort. I did the same thing, but using the same value in each of the RGB channels, instead of using the CMYK method. All this does is trick Color Port to expect a neutral gray and export the correct Lab values in the measurement file.
You will need create your own by loading the same luminance values into each of the RGB values for tones 0-255. Create a new target to save as a tiff, which you then print with no color management through PrintTool. Then measure the target in ColorPort, and save the measurement data as tab delimited and Lab values.
Being confined to the ColorPort patch layout is frustrating, wasting lots of paper with the way the patches wrap to the next line and I miss the ease of defining and measuring targets in Measure Tool. It rarely was unable to read a patch strip, ColorPort gives all sorts of errors when laying day "too much" ink. I keep around a Snow Leopard partition for this very reason. MeasureTool and ColorLab are indispensable for converting spectral data to Lab and several other formats or then converting to density.
I will see if I can load the reference file and stepwedge up to the files section here. If not, I will get to posting them to my site for download later in the week
Hope this helps.
Richard Boutwell
www.RichardBoutwell.com
www.BWMastery.com