Created attachment 611448 [details] Screenshot of this issue reproducing Mozilla/5.0 (Windows NT 6.1; rv:12.0) Gecko/20100101 Firefox/12.0 Mozilla/5.0 (X11; Linux x86_64; rv:12.0) Gecko/20100101 Firefox/12.0 Mozilla/5.0 (Macintosh; Intel Mac OS X 10.6; rv:12.0) Gecko/20100101 Firefox/12.0 BuildID: 20120328051619 Steps to Reproduce: 1. Launch Firefox. 2. Open multiple tabs.(The more tabs are opened the easier the issue reproduces.) 4. Close the tabs one by one quickly (middle click, click the "X" button, or press Ctrl+W). For many of the closed tabs, when a tab is closed, an empty unresponsive titlebar remains on the tabs bar for 2-7 seconds. - Please see the attached screenshot for more details.
This bug might have been provoked by the fix for bug 585813.