Stumbled on to this one by accident while remarking the generally lovely way we now behave wrt to active/inactive window state on Mac since bug 406730 landed. STR: 1) Visit a page with a bad SSL cert, e.g. https://paypal.com 2) Click add exception, and retrieve the certificate (don't dismiss the dialog!). 3) Click the "View" button to view the certificate 4) Close the cert viewer 5) Cancel the exception dialog Result: The title bar of the browser continues to reflect active state, but the chrome and contents appear inactive. Swapping away and back to the app restores normal active state.