Curves Tool

[marvpelkey]

Recently updated Photoshop, pursuant to a notice from Adobe.
Now, when I use a Curves Adjustment layer, and drag the dropper (via the mouse left button) in the image, the image will not change until I release the mouse button.
When the button is released, there will be an immediate (and often severe depending on how much the dropper is moved) change to the image.
I seem to recall, pre update, that the image tone changed as the dropper was being moved.
I also recall that moving a Levels slider would also cause the image to change while moving the slider (rather than wait until the mouse button was released). That action remains unchanged, and it only seems to be the Curves that has changed.
Can someone advise if Curves has actually changed or if it is just my machine, and if it is my machine, how I can get it to revert to "normal" activity.
Thanks

[digitaldog]

What you report is NOT normal; the edit should update on the fly. It might be a GPU issue or a setting. Check to see if your hardware is up to snuff, check the general preferences for GPU settings, or maybe trash your preferences.

[marvpelkey]

Thanks very much for the reply.
The computer is fairly new and has been fine since purchase, and this issue only occurred immediately after the update. I will check the things you have suggested.