The padlock icon shown when entering secure sites using Firefox 3.x is not displayed using Firefox 4. How can this be restored? Is it indicating another problem?

It has been changed. Please read this article: https://support.mozilla.com/en-US/kb/Site%20Identity%20Button You can use this add-on to get the classic icon back: https://addons.mozilla.org/en-US/firefox/addon/padlock-icon/