H Andrew
I had the same files on my windows laptop and while ACR is open, the RGB numbers will constantly display the numbers of the pixel under the cursor.
In the Imac, at the time a file is just open in ACR the RGB numbers display some values, like: R: 125 G: 201 B: 85, but after I move the cursor a bit, instead of updating, the numbers disapear and I just see R:- G:- B:-
Everyting else in Camera Raw seem to work fine, I think.
New computer and first time using a MAC
Hugo