User-Agent: Mozilla/5.0 (Windows; U; Windows NT 6.0; en-US; rv:1.9) Gecko/2008051206 Firefox/3.0 Build Identifier: Mozilla/5.0 (Windows; U; Windows NT 6.0; en-US; rv:1.9) Gecko/2008051206 Firefox/3.0 If you have Firefox 3.0 RC1 set to prompt each time a website tries to set a cookie, and you are dragging-and-dropping a tab or a bookmark at the *exact* time the cookie allow/deny dialog box appears, both the window you are dragging-and-dropping the bookmark/tab on, and the cookie prompt, will become 'frozen.' Specifically, neither will respond to any clicks, including the Close button, and right-clicking the window's tab in the Taskbar will not present a menu to close the window. Only terminating firefox.exe and relaunching will resolve the problem. Reproducible: Always Steps to Reproduce: 1.) Set Firefox 3.0 RC1 to prompt you every time a website tries to set a cookie. 2.) Visit a new website which sets cookies and you currently have no cookie acceptance policy for. 3.) Before the prompt to allow/deny the cookie appears, begin to drag-and-drop a tab or a bookmark. (Act quickly!) ALTERNATIVELY: 1.) Set Firefox 3.0 RC1 to prompt you every time a website tries to set a cookie. 2.) Bookmark a website, leave the website, and then delete its cookie acceptance policy. 3.) Open Organize Bookmarks (Library). 4.) Begin to drag-and-drop the newly-created bookmark. Actual Results: The respective windows/dialog boxes became 'frozen,' as if disabled or unfocusable. Expected Results: Firefox 2.0.x handled this fairly well, automatically granting the cookie prompt focus, flashing the dialog box, and playing the system default sound. Reproduced on three separate installations/machines, two of which had clean profiles with no extensions or themes installed.
If you don't use microsummaries you could set browser.microsummary.enabled to false in about:config.