I've read the online help, but I can't seem to get the in-comp HUD gizmo-widget-thing to appear when working with a Shape Layer's gradient fill.
I can only modify gradients numerically in the timeline. I've toggled the mask/shape path visibility button, and of course the layer and shape is selected.
I've seen it before, so I'm obviously missing some step.
CS6 11.0.2, OS X 10.6.8, Quadro 4000.
Show a screenshot of your UI so I can see what you're trying/doing.
My first guess is that you're not using the Selection tool.
Also the visibility of that thing depends on how you group shape stuff and which component is selected...