User-Agent: Mozilla/5.0 (Macintosh; U; Intel Mac OS X 10.4; en-US; rv:1.9.1b1pre) Gecko/20080930073353 Minefield/3.1b1pre Build Identifier: Mozilla/5.0 (Macintosh; U; Intel Mac OS X 10.4; en-US; rv:1.9.1b1pre) Gecko/20080930073353 Minefield/3.1b1pre By dragging a single tab from a window on top of the others to the far right of the window behind it the window with one tab be dragged away is closed (as expected) but it changes the page of a tab below it and creates a dummy tab of "Untitled" which cannot be closed as an ordinary tab should be. Reproducible: Always Steps to Reproduce: 1. Create a new profile 2. Open 3 tabs: google.com, mozilla.com, gnu.org in a full size window 3. Open a new window which should bring you to http://www.mozilla.org/projects/minefield/ 4. Resize so you can see the tab bar of the window underneath. 5. Drag http://www.mozilla.org/projects/minefield/ from the window on top to the far right of the tab bar on the window below with the three tabs already open Actual Results: The new tab becomes a page called "Untitled" which cannot be closed. The previous third tab (gnu.org) becomes http://www.mozilla.org/projects/minefield/. The untitled tab cannot be closed by click the X or by using the "close tab" shortcut key. You must close all other tabs first to be able to close it. Expected Results: Your first three tabs should remain unchanged and http://www.mozilla.org/projects/minefield/ should open on the far right as a fourth tab.