Adobe Photoshop question...

[tuzz]

I'm trying to adjust the curves for an image, in Edit > Adjust > Curves but the problem is that when I open up the dialog box to adjust the curve, all I get is a black box where there should be a gray box with the curve to adjust. Anyone got any ideas on how to fix this so I can adjust the curves?

 

[tuzz]

That should be Image > Adjust > Curves above.