QTR-Quadtone RIP

I am using QTR Create ICC with great success, printing through PS CS2.  
I have noticed, however, that earlier versions of PS (I have tried 6 
and CS) "experience" the profiles as "invalid" and will not print 
through them.  These PS versions also declare the profile invalid in 
attempting to use them in the Soft Proof mode.  I didn't know if others 
were aware of this (or indeed if it is important, except that a lot of 
people are still using CS).