Help - out of gamut colours / borked palette?

[brulleks]

Yes, that was one of the first things I tried. I've switched between all settings on the palette itself, but it's still there.

I did quite a lot of tinkering with the settings before finally giving up and reinstalling/deleting the profile.

I really don't understand how it can persist with a brand new installation and profile. I even went through the registry deleting all references to GIMP before reinstalling!