converting to greyscale flips my curves

[gongman5000]

Every time I convert an image/psd/tif to greyscale inside photoshop or in ACR my levels sliders and curves are inverted such that whites are on the left and blacks are on the right and everything is upside down (raising the curve on the black side lowers the blacks, lowering curve on white side raises the whites etc). This never happened to me before but happens every time now, I'm not sure what button I've hit to make photoshop do this and can't seem to figure it out. Any help is greatly appreciated

 

[Steve]

In Curves Display Options on the bottom of the curves pallet click on Show Amount Of: Light