GIMP odd behaviour Some parts don't work

[jeanlinux]

Hello everyone,

Nice to meet the group. This is my first post. Hope I am doing things the right way !

I have recently noticed that in the COLOUR list of possibilities a great many are not operating any more, except Contrast/ Levels and Curves. How come?

My first idea was to un-install the whole of GIMP and re-install. But it was to no avail.

I'm at a loss what to do.


My OS is Windows 10 -64bit, I have 16 GB or RAM. 

Thank you for your help ans suggestions.

Jean