By default, QuarkXPress 8 will switch you to edit mode when you double-click a box.
You can change that behavior back to the old “open the Modify dialog box” behavior in Preferences> Print Layout> Tools.
Jay Nelson is the editorial director of PlanetQuark.com, and the editor and publisher of Design Tools Monthly. He’s also the author of the QuarkXPress 8 and QuarkXPress 7 training titles at Lynda.com, as well as the training videos Quark includes in the box with QuarkXPress 7 . In addition, Jay writes regularly for Macworld and Photoshop User magazines and speaks at industry events.