CMYK gradient maps don't work correctly in Photoshop CS 4

Question

Gradient maps built with CMYK colors in Photoshop don't work correctly in CS4.  For one particular client I often use a brushed steel background. To control color shifts on the press I used a gradient map blending from C0 M0 Y0 K0 to C40 M20 Y20 K100. This has worked great in the past, but once you open that gradient map in CS4 and start editing that gradient at all, even if you edit it back to the original CMYK numbers, the colors shift drastically, and if you watch the info palette, the colors get totally remapped to a different black. I can go in a reset the black to the C40 M20 Y20 K100 mix, but it doesn't work. When I go back in, it completely changes them.
Since this works fine in CS3 and not in CS4, is this a program bug? I'm not doing anything differently.
It was a great way of controlling neutral gray mixes (and other color mixes) for CMYK printing. Is there a fix for this? Adobe, is anyone addressing this bug? I've read other threads on this, but with no solutions.
Kent Bingham
Digital Illustration and Design
I couldn't attach the .psd files, so I uploaded here for reference:
http://www.kentbingham.com/gradientmap-error.zip

Answer 1

I have not gone back to check how this is handled in CS3 yet I could duplicate your problem in CS4.  The changing of numbers in the CMYK looks like it has to do with the color mangement settings in Photoshop.
I was able to make sure the numbers input to the gradient map did not chang.  I did this by going to Edit>Assign Profile  and then clicked the option "Don't Color Manage this Document"    
This may not solve your problem directly yet it does indicate that the problem you have (or that Adobe has) is related to how the color management is being handled.
So one question would be are you using the "exact" color management settings in CS4 as you did in CS3 and were those in place when you imported the file into CS4.  If not, and if you did not have the correct warning options set, there may have been a color setting change of which you were not aware.
While I was able to keep the original settings from changing in the Gradient Map, there was still a problem in CS4 where the Lab values would change (and the appearance on the LCD screen) after doing any color picker editing and changing the CMYK values back to 40 20 20 100.  This definetly seems related to the color model/probile/management system in place.  So it appears that even though I can get the CMYK numbers to stay and not change, there is still a bug when making no changes to the color management settings, and the CMYK values are the same, that the Lab values and the appearance on the screen change.
Hope you can get Adobe's attention.  Looks like a bug to me.