Graeme, are you aware of this problem ? It might be better to not output any value instead of a constantly broken value.
It's not a "problem", it's the nature of the instrument. It only has a single (hence monochrome) sensor for ambient light (the little grey "bump" on the back). Naturally it can't report a color temperature from it. (I'll modify spotread to not report the CCT in this case).
I was also wondering the "real" difference between huey and hueyPro : Pantone is saying they "upgrade" the sensor firmware but I have some doubts about that and I guess that is their way of "selling" a pure software upgrade (which is not needed for argyllcms luky users ..).
Hard to say without an instrument to play with. I would be a bit surprised if the instrument itself was different, but it's possible of course, and it isn't driven quite the way the i1d2 is driven. Graeme Gill.