Hi
Can you show a screenshot with the layers panel visible and the image window immediately before making the image adjustment?
You might also want to try a preference reset in the meantime. Go to Preferences >General > Reset Preferences on Quit. You will need to restart Photoshop after clicking OK.
Dave
I have uninstalled and reinstalled PS and the problem has been cleared up. Everything else I use on a regular basis was working fine, but obviously there was some small glitch in the installation. Thanks you all for he responses