Hi, I've been playing in brush settings all morning and I just held down a few keys (Ctrl+Z I thought) but must have held down something else and now my brush settings control panel is all greyed out and I can't use it.
You did really well providing the screen shot, but it would be more useful if you'd shown the entire workspace. If you can do that I'm sure we can sort it out. Leave it at full res, and show layers panel, an history panel at least. Have the brush tool selected.
I agree with what @Trevor.Dennis said, but just in case, (and to reiterate what Trevor said) make sure you have the brush tool selected when you go into the Brush Settings Panel. Otherwise, yes - everything will be greyed out as you see here. If you hit CTRL+Z, it might be you went back to where you were before you had selected a brush in the first place.