Did what is a window change?

With the GIMP you can take a screenshot of a window.

So when working on a multimedia guide for F18, I needed screenshots of grip - and I wanted one of the option menus on the preferences pane active.

Set up GIMP to do screenshot of just a window, made grip the active app, and clicked on the preference for encoder.

What I got was a screenshot of the menu, not grip with the menu on it.

Um, what? That use to never happen. Is gnome changing the way menus work so they look like their own window to the xserver?

I'm confused.