Photoshop :: What Are Conditions That Make OpenCL Unavailable

Up to 2 days ago I had ATI Catalyst 12.2 installed. I was able to check all the boxes in the Advanced Graphics Processor Settings dialog and they stayed set. Specifically, I had [ ] Use OpenCL set and Photoshop CS6 worked very well.
 
Because I need to know about the quality of newer drivers for my own product development, I upgraded my ATI driver suite to the current version - Catalyst 12.4.
 
Unfortunately, this caused new problems I hadn't had before - specifically a number of GPU-accelerated features didn't work, such as Oil Paint, which would appear to try to start then just exit a split second later.  And with Catalyst 12.4 the [ ] Use OpenCL setting became unavailable (grayed-out).
 
With my own testing done, I decided to completely uninstall the ATI Catalyst 12.4 suite, and drop back to Catalyst 12.2.
 
This was a simple matter of uninstalling everything AMD then rebooting (with the Windows driver), then installing Catalyst 12.2. That went smoothly. However, now I still do not find the [ ] Use OpenCL box has become available again - it's grayed out:
 
there are no remnants from the 12.4 drivers left on my system (though there's a possibility I could have missed something), and everything from the 12.2 set installed successfully, so the question is this:
 
Did Photoshop sense something about the 12.4 driver set, then set some kind of permanent "No OpenCL" flag in its own configuration settings? Here's my system info with the 12.2 drivers installed. Note the "OpenCL: Unavailable" entry. URL....
 
Note that all my GPU-accelerated features seem to work...  Oil Paint works and is plenty fast, the various Blur tools work nice and fast, I can do 3D rendering (though there's one small glitch I've had since Photoshop CS6 was released where occasionally it becomes unresponsive for a few seconds at a time while doing 3D work).  But it does finally respond.