A certificate is required to access a certain financial institution. I used this certificate to access the website with the previous version of FF on a daily basis. However, immediately after upgrading to FF4 I received the error message found in the question, along with "The page you are trying to view can not be shown because the authenticity of the received data could not be verified" after providing answers to the standard security questions. I've transferred the certificate to IE for now, which works fine, but I'd like to use FF4 so I can do all my tasks through one browser, naturally. Thanks for any help you can provide. It's genuinely appreciated. John